Alexander v Minister for Home Affairs [2022] HCA 19 | Case summary

Alexander v Minister for Home Affairs [2022] HCA 19 | Case summary | Zoe

On 16 April 2013, Mr Alexander departed Australia for Turkey, indicating on his outgoing passenger card that he would be overseas for three months. He had informed his family that he intended to arrange a marriage and that he would return to Australia. Having entered Turkey, at some point Mr Alexander travelled to Syria, where he married his wife.
The Australian Security Intelligence Organisation ("ASIO") reported in June 2013 that Mr Alexander's travel to Syria was facilitated through a Sydney‑based network developed by Mr Alqudsi, who had previously been charged with terrorism‑related offences[1]. Mr Alexander was reported to be part of a group that was taken to Syria by a senior Syria‑based Australian member of the Islamic State (also known as "ISIL" or "ISIS"). At this time, the Islamic State had been designated in the Criminal Code (Cth) (under various names) as a terrorist organisation. ASIO later reported that it was "likely" that Mr Alexander had joined ISIL by August 2013, and that he had "likely engaged" in foreign incursions and recruitment by entering or remaining in al‑Raqqa Province in Syria on or after 5 December 2014.
In November 2017, Mr Alexander was apprehended by Kurdish militia in the village of Ziban in Deir El‑Zour Province in Syria (which was not a declared area). In March 2018, he was transferred to the custody of Syrian authorities and was subsequently charged by Syrian prosecutors with offences against the Syrian Penal Code.
On 31 January 2019, Mr Alexander was convicted and sentenced by a Syrian court to a term of imprisonment for 15 years - subsequently reduced to five - on the strength of admissions he had made during an interrogation. However, Mr Alexander's sister, who appears as his litigation guardian in these proceedings, stated that Mr Alexander told her that he was tortured and forced to sign a paper while in the custody of the Kurdish militia and Syrian authorities without reading its contents.
By reason of a pardon from the Syrian government, Mr Alexander's term of imprisonment has expired. However, he remains in detention for a number of reasons, including that he cannot be released into the Syrian community, nor can he be repatriated to Turkey or Australia.
On 13 July 2020, Mr Alexander was moved to the prison known as Far' Falastin, or Branch 235, which is located in Damascus and operated by Syrian intelligence authorities. For the duration of the conflict in Syria, there have been reports of government forces arbitrarily detaining persons simply for being perceived to be opponents of the State, including in Kurdish territory where persons are suspected of affiliation with the Islamic State. The detention of prisoners in government‑controlled prisons in Syria has been associated with serious human rights violations, including torture.
Since 15 July 2021, neither Mr Alexander's family nor his lawyers have been able to contact him. Mr Alexander claims that, according to his Syrian lawyer, the fact that he is no longer an Australian citizen is a reason for his continuing detention.

Following Mr Alexander's arrival in Syria, the Australian government made several decisions in relation to him leading up to the determination of his citizenship. On 5 September 2013, the then Acting Minister for Foreign Affairs decided to cancel Mr Alexander's passport under s 22(2)(d) of the Australian Passports Act 2005 (Cth). That was on the basis that ASIO suspected on reasonable grounds that "if an Australian passport were issued to [Mr Alexander], [Mr Alexander] would be likely to engage in conduct that might prejudice the security of Australia or a foreign country"[2]. This decision did not affect his status as an Australian citizen, or any entitlement that he may have had to Australian citizenship or consular assistance.
On 19 June 2020, the Minister made a Temporary Exclusion Order ("TEO") in respect of Mr Alexander, pursuant to the Counter‑Terrorism (Temporary Exclusion Orders) Act 2019 (Cth). The effect of the TEO was to prevent Mr Alexander from entering Australia while it remained in force, which was until 30 January 2022.
On 16 June 2021, the Director‑General of Security at ASIO provided a Qualified Security Assessment ("QSA") of Mr Alexander to the Minister. The purpose of the QSA was to advise whether it would be consistent with the requirements of security for prescribed administrative action to be taken under the Citizenship Act in respect of Mr Alexander. Although ASIO, in the QSA, did not make any recommendation in relation to Mr Alexander's citizenship, it stated that, if the Minister were satisfied that Mr Alexander had engaged in specified conduct and that conduct demonstrated that he had repudiated his allegiance to Australia, the Minister might make a determination in writing that he ceased to be an Australian citizen.
The QSA stated that, based on "substantial classified reporting and some unclassified corroborating information", ASIO assessed that Mr Alexander "likely engaged in foreign incursions and recruitment by entering or remaining in al‑Raqqa Province in Syria, a declared area, on or after 5 December 2014" and "likely travelled to Syria in early‑to‑mid‑2013, and had joined the Islamic State of Iraq and the Levant ... by August 2013".
On 2 July 2021, the Minister determined, pursuant to s 36B(1) of the Citizenship Act, that Mr Alexander ceased to be an Australian citizen. The determination stated that the Minister was satisfied that: Mr Alexander had engaged in foreign incursions while outside Australia[3], which demonstrated a repudiation of his allegiance to Australia[4]; that it would be contrary to the public interest for Mr Alexander to remain an Australian citizen[5]; and that Mr Alexander would not become stateless by reason of the determination[6]. In making that determination, the Minister relied, in part, on the QSA. The Minister was not required to, and did not, give a statement of reasons for the determination.

Citizenship, as formal membership of the national community, is a statutory concept[22]. It is the grant of Australian citizenship that creates the status which attracts constitutional protections and engages federal and State legislation that confers or denies rights, privileges, immunities or duties[23]. Relevantly for Mr Alexander, the status of Australian citizenship includes the right to enter and remain in Australia[24], the entitlement to an Australian passport[25], and the right and duty to vote in federal elections[26].
Citizenship is not a concept used in the Constitution (save for s 44(i), which is concerned with foreign citizenship). The Constitution, in contrast to the first clause of the Fourteenth Amendment to the Constitution of the United States, does not contemplate that individuals born here are citizens of Australia, much less that they are indelibly so. This Court's decisions in Singh v The Commonwealth[27] and Koroitamana v The Commonwealth[28] would be plainly misconceived if, as a matter of constitutional law, a person born in Australia has for that reason, and quite apart from any law of the Parliament, a right to live here. Mr Alexander's counsel made no attempt to challenge the correctness of Singh and Koroitamana.
While alienage, describing a lack of formal legal relationship with the community or body politic, is a constitutional concept[29], the Constitution leaves it to Parliament to decide who shall be granted the status of citizenship and what that status may mean in terms of the rights, privileges, immunities and duties of citizens. In this regard, s 51(xix) of the Constitution empowers the Parliament to "create and define the concept of Australian citizenship"[30], to select or adopt the criteria for citizenship or alienage[31] and to attribute to any person who lacks the qualifications prescribed for citizenship "the status of alien"[32]. In Chetcuti v The Commonwealth[33], Kiefel CJ, Gageler, Keane and Gleeson JJ said that "the aliens power encompasses both power to determine who is and who is not to have the legal status of an alien and power to attach consequences to that status".
It has been said in this Court that the terms "citizen" and "alien" are antonyms[34]. Recently, the majority of this Court in Love v The Commonwealth[35] held that Aboriginal Australians who satisfy the tripartite test in Mabo v Queensland [No 2][36] constitute a separate category of non‑citizen, non‑alien, and that "non‑citizen" is not inevitably and always synonymous with "alien". But in Chetcuti, Kiefel CJ, Gageler, Keane and Gleeson JJ observed that this Court's decision in Shaw v Minister for Immigration and Multicultural Affairs[37] (from which the holding of the majority in Love does not depart, except in respect of an Aboriginal Australian according to the tripartite test in Mabo [No 2]) establishes that the aliens power supports a law of the Commonwealth which determines who shall have the status of Australian citizenship, and which provides that persons who do not share that status are aliens[38].
In Pochi v Macphee[39], Gibbs CJ said that "Parliament cannot, simply by giving its own definition of 'alien', expand the power under s 51(xix) to include persons who could not possibly answer the description of 'aliens' in the ordinary understanding of the word". It does not stretch the ordinary understanding of the expression "alien" to include within that category an individual who has engaged in conduct exhibiting such extreme enmity to Australia as to warrant being excluded from membership of the Australian community. The Parliament has the power under s 51(xix) to attribute the constitutional status of alien to a person who has lost the statutory status of citizenship. By the same power, Parliament can define the circumstances in which that occurs.
There is ample support in authority for the view that the scope of s 51(xix) extends to permit Parliament to "determine the legal basis by reference to which Australia deals with matters of nationality ... to create and define the concept of Australian citizenship [and] to prescribe the conditions on which such citizenship may be acquired and lost"[40]. Mr Alexander's contention that a person who becomes an Australian citizen is thereby beyond the scope of the power that permits Parliament to make laws that deprive that person of citizenship is distinctly inconsistent with the following passage in Nolan v Minister for Immigration and Ethnic Affairs[41], where Mason CJ, Wilson, Brennan, Deane, Dawson and Toohey JJ said:

Mr Alexander argued that it was not open to the Parliament to treat the conduct described in s 36B(5)(h) as a repudiation of his allegiance constituting sufficient reason for depriving him of his citizenship.
In response, the Solicitor‑General of the Commonwealth, appearing for the defendants, cited examples[58] of laws, the validity of which has never been challenged, that provide for the loss of citizenship as a result of acts indicating either loyalty to a foreign state or disloyalty to Australia. It was submitted that s 36B is "of the same genus" as some of those laws[59], save to the extent that s 36B encompasses disloyalty indicated by a willingness to engage in terrorist activity in a foreign state. Specifically, the conduct captured by s 36B(5)(h) was characterised as "inherently suggestive of the absence of a continuing commitment to the Australian body politic". There is force in the Solicitor‑General's submissions.
The absence of the continuing commitment that is citizenship is sensibly described as an absence of "allegiance". The utility of "allegiance" as a determinative test for non‑alienage has been questioned[60]; and the plurality in Chetcuti held that the reach of the aliens power could be determined in that case "without need to explore common law notions of allegiance and alienage"[61]. But allegiance is a useful gauge of the existence of the bonds of citizenship. Section 44(i) of the Constitution itself expressly acknowledges that allegiance may be an integral aspect of citizenship.
Given that citizenship is a status of reciprocal rights and obligations, it is to understand the status of citizenship in an incoherently one‑sided way to say that s 51(xix) supports a law that specifies the criteria by which a citizen may voluntarily renounce Australian citizenship - as Mr Alexander accepted - but does not support a law that treats voluntary conduct demonstrating a repudiation of allegiance to Australia as an implied renunciation of citizenship.
Mr Alexander argued that voluntary conduct of the kind described in s 36B(5)(h) cannot rationally be treated as a repudiation of allegiance unless it is intended to be so. The facts stated in the special case suggest that it was reasonably open to the Parliament to regard voluntary conduct, as described in s 36B(5)(h), as so reprehensible as to be incompatible with the common bonds of allegiance to the Australian community, even though the person who has engaged in that conduct did not act intentionally to repudiate the bonds of citizenship. It is convenient to turn now to refer to those agreed facts.

On 4 December 2014, the Minister for Foreign Affairs made a declaration pursuant to s 119.3(1) of the Criminal Code (Cth) that al‑Raqqa Province in Syria was a "declared area"[62], on the basis of information indicating that it was the de facto capital of the Islamic State's operations and was used to engage in hostile activities. That declaration was revoked on 27 November 2017 on the basis that it was no longer confirmed that the Islamic State was engaging in hostile activity there[63]. It may be noted that Deir El‑Zour Province in Syria (where Mr Alexander was apprehended by Kurdish militia forces) was not a declared area.
The Islamic State has been listed as a "terrorist organisation" within the meaning of para (b) of the definition in s 102.1(1) of the Criminal Code (Cth) under various names since at least 2010, including "Al‑Qa'ida in Iraq", "Islamic State of Iraq and the Levant" and "Islamic State"[64]. In 2016, it was also listed as a "declared terrorist organisation" for the purposes of former s 35AA of the Citizenship Act[65].
Since 2015, the terrorism threat in Australia has been assessed by ASIO as "Probable" on the National Terrorism Threat Advisory System, signifying that credible intelligence, assessed by Australia's security agencies, indicates that individuals or groups continue to possess the intent and capability to conduct a terrorist attack in Australia. The threat of religiously motivated violent extremism, including from groups such as the Islamic State, was and remains the principal concern[66].
Since 2014, there have been at least nine attacks targeting people in Australia and 21 major counter‑terrorism disruption operations in response to attacks being planned in Australia, such as the actions of Man Haron Monis in taking 18 people hostage at the Lindt Café in downtown Sydney.
In March 2019, the Islamic State was ousted by the United States‑led Global Coalition to Defeat Islamic State from the last of the territory it had controlled across Syria and Iraq. While ASIO reported that "ISIL's 'caliphate' has been crushed and it has lost its safe havens and organised military capability", it identified that any remnants remained dangerous and required ongoing attention, including the anticipated return to Australia of foreign fighters[67]. Similarly, US intelligence considered that, as at April 2021, the Islamic State remained capable of waging a prolonged insurgency in Iraq and Syria and leading its global organisation, despite compounding senior leadership losses.
The risk posed by foreign fighters, defined by ASIO as "Australians who have participated in foreign conflicts or undertaken training with extremist groups overseas", is an aspect of this general threat. While relatively few returned fighters have posed a direct risk to the Australian community, those that did have been responsible for some of the most lethal terrorist attacks.
ASIO has reported that, since 2012, around 230 Australians (or former Australians) have travelled to Syria or Iraq to fight with or support groups involved in the Syria‑Iraq conflict. Of that, 50 are estimated to have returned to Australia, the majority before 2016.
In a submission to the Parliamentary Joint Committee on Intelligence and Security's 2019 review of the Australian Citizenship Amendment (Citizenship Cessation) Bill, ASIO continued to assess that the return of Australians who have spent time with Islamist extremist groups in Syria or Iraq has the potential to exacerbate the Australian threat environment "for many years to come"[68]. This is because foreign fighters can be expected to have developed characteristics such as a greater tolerance for and propensity towards violence, and to have established jihadist credentials[69]. Several serious terrorist plots in Australia between 2000 and 2010 each involved at least one returned foreign fighter.

Mr Alexander argued that s 36B of the Citizenship Act reposes in the Minister the power to adjudge and punish criminal conduct by involuntary denaturalisation. This was said to be an exclusively judicial function, and not one which fell within any established exception bringing it within the acknowledged remit of the executive.
In support of this submission, Mr Alexander relied upon Chu Kheng Lim v Minister for Immigration, Local Government and Ethnic Affairs[70]. Mr Alexander sought to characterise denaturalisation as punishment.
The defendants accepted that the function of "adjudging and punishing criminal guilt" is "exclusively judicial", as this Court held in Lim[71]. But the defendants submitted that Lim said nothing about laws that do not impose detention in custody[72], of which s 36B is one.
The defendants submitted that at its highest, s 36B confers a power to inflict "involuntary hardship or detriment" on a person, which, as Gleeson CJ explained in Re Woolley; Ex parte Applicants M276/2003[73], is "not an exclusively judicial function". Further, it was submitted that it was not necessarily the case that deprivation of Australian citizenship would inflict hardship or detriment, particularly because s 36B allowed the cessation of citizenship only in the case of a person who is also a citizen of another country.
The defendants also emphasised that s 36B is a discretionary power based on three conditions: that the person has engaged in the requisite conduct (as specified by s 36B(5)); the conduct demonstrates that the person has repudiated his or her allegiance to Australia; and that it would be contrary to the public interest for the person to remain an Australian citizen. The defendants also sought to emphasise that the power was ultimately discretionary, and that a determination under s 36B, and any decision to refuse to revoke it, is subject to judicial review.
The submissions of the defendants should not be accepted. The consequences of a determination under s 36B for the citizen, the legislative policy which informs the operation of s 36B, and a comparison of the operation of s 36B with the provisions of s 36D (which authorise the same consequences for the citizen only upon conviction after a trial), all point to the conclusion that the power reposed in the Minister by s 36B(1) is a power which Ch III of the Constitution requires to be exercised by a court that is part of the federal judicature. To these considerations one may now turn.

Visnic v Australian Securities and Investments Commission[87] and Australian Communications and Media Authority v Today FM (Sydney) Pty Ltd[88] were cited by the defendants' counsel in support of the argument that a determination under s 36B is neither an adjudgment of guilt nor an imposition of punishment. Crucially, these cases dealt with the revocation of licences or other statutory privileges, rather than citizenship. These cases are examples of the point that the hardship or detriment involved in the revocation of a statutory licence or other privilege, where the holder of the licence or privilege is shown to be not a fit and proper person to enjoy the privilege or the licence, is not "punishment", which is an exclusively judicial function. But the punishment of an individual involving the deprivation of citizenship by reason of that person's misconduct is punishment of a different order from the loss of a statutory privilege or a licence under a regulatory regime. The consequence for a person who voluntarily does the acts described in s 36B(5)(h) is no different in substance from the punishment meted out pursuant to s 36D. Such a consequence cannot be equated with the cancellation of a licence or other privilege conferred by a statute which regulates business or other activities.
In Kennedy v Mendoza‑Martinez[89], Goldberg J, writing for the majority of the Supreme Court of the United States, held that a law depriving a citizen of the United States of his nationality for evading conscription for military service was constitutionally invalid on the basis that it imposed "the sanction of deprivation of nationality as a punishment ... without affording the procedural safeguards ... [of] trial by duly constituted courts". The majority opinion in Kennedy recognised that the deprivation of the rights of citizenship serves to "promote the traditional aims of punishment - retribution and deterrence"[90]. As Brennan J said in his concurring opinion[91], so it may be said of s 36B(1) that the sanction of "expatriation" is "available for no higher purpose than to curb undesirable conduct, to exact retribution for it, and to stigmatize it".
As was said in Lim, whether a law provides for the adjudication and punishment of criminal conduct is a matter of substance, not form[92]. The substantive effect of the deprivation of rights of liberty conferred by Australian citizenship is not disguised by the use of the emollient language of "citizenship cessation" to describe the effect of a determination under s 36B upon an individual. In this regard, it may be noted that s 40(2) of the British Nationality Act 1981 (UK) provides, with commendable frankness, for the "deprivation of citizenship" of an individual if the Secretary of State is satisfied that deprivation is conducive to the public good. The candid language in which this provision is expressed acknowledges the substance of the effect of the ministerial determination upon the citizen in question. This candour may owe something to the circumstance that the validity of the conferral of such a power on the executive government of the United Kingdom is not dependent on conformity with constitutional requirements such as those found in Ch III of our Constitution; but however that may be, the British Nationality Act more accurately expresses the effect upon the citizen of a determination under s 36B than "citizenship cessation".

Section 36D, like s 36B, gives practical effect to the policy stated in s 36A. Each provision serves "to shore up the convictions of the law‑abiding by demonstrating that the wicked will not go unscathed"[94] for the reprehensible conduct described in ss 36B(5)(h) and 36D(5)(g).
The sanction of deprivation of citizenship may be imposed upon an individual by the exercise of the discretion conferred on the Minister by s 36B rather than as a consequence of a conviction after a trial under s 36D. True it is that the Minister under s 36B need not be satisfied of the same mental elements necessary to establish the commission of an offence under s 36D[95], but to say this is to draw attention to the lower factual threshold required by s 36B for the exercise of the power reposed in the Minister to effect a deprivation of citizenship. It also highlights the absence of the procedural safeguards attending a criminal prosecution of an offence under s 36D.
Both ss 36B and 36D deal with the topic of "[c]essation of citizenship on determination by [the] Minister". But in the case of s 36D, the power of the Minister arises only in relation to a person who has been convicted and sentenced of an offence or offences by a court[96]. In contrast, the Minister's discretion under s 36B arises upon the Minister him or herself being satisfied that the conduct elements of the offence have occurred. And the Minister may be satisfied of those matters in circumstances in which the "offender" has not had a fair hearing (or indeed any hearing at all), much less the benefit of the other safeguards of a criminal trial, including the incidence of the burden of proof.
Statute law may validly regulate the incidence of the burden of proving facts without offending Ch III of the Constitution[97], but s 36B contemplates a process of ministerial fact finding in relation to the grounds for the deprivation of citizenship in which the State is not required to carry the burden of proof, by contrast to the position under s 36D. Indeed, under s 36B, the Minister is not required even to proceed in accordance with the rules of procedural fairness[98]. And yet the process under s 36B may result in the same outcome by way of deprivation of citizenship as under s 36D, where the protections afforded by a criminal trial have been afforded to the citizen. This incongruity is not dispelled by the possibility that an application for revocation may subsequently be made under s 36H or that s 36J or s 36K may be engaged.
Some reference to the evolution of s 36B is also illuminating. Provisions for the termination of citizenship on terrorism‑related grounds were first introduced into the Citizenship Act by the Allegiance to Australia Act and commenced on 12 December 2015. These provisions were introduced as part of the government's response to the Review of Australia's Counter‑Terrorism Machinery for a Safer Australia, and with a view to broadening powers relating to the cessation of Australian citizenship for persons engaging in terrorism and who were a serious threat to Australia and Australia's interests[99].
The predecessor to s 36B was s 33AA of the Citizenship Act. It was in largely the same terms, except that it provided for a mental element[100]:

Constitutional analysis in a variety of contexts can be assisted by identifying the "purpose" (or "object" or "end") of a law as distinct from the "manner" (or "means" or "mechanism") by which the law is designed to achieve that purpose. Without being exhaustive, those contexts include determining whether a law is "with respect to" a designated topic of legislative power[105], determining whether a law infringes the express guarantee of freedom of interstate trade[106] or intercourse[107], and determining whether a law infringes the implied guarantee of freedom of political communication[108].
In each context, the "purpose" is the "public interest sought to be protected and enhanced" by the law[109]. Expressed in more arcane terms, the "purpose" is the positive counterpart of "the mischief to redress of which [the] law is directed"[110].
The purpose of any law can be described at different levels of generality. At one extreme, a law made by the Commonwealth Parliament under s 51 of the Constitution can always be described in the opening words of that section as being "for the peace, order, and good government of the Commonwealth". At another extreme, the same law can be described as having the specific purpose of achieving exactly what the law does. For example, the purpose of s 36B can be described as being to cancel the Australian citizenship of a person if the statutory preconditions it specifies are met and if the ministerial discretion it confers is exercised. Neither description is incorrect. But neither is of much use in constitutional analysis.
Between those two extremes will often lie other available descriptions each having a different level of generality. The selection between those other descriptions will then be functional. The level of generality at which the purpose of the law is best described will depend on what constitutional analysis is being undertaken. That in turn will depend on what constitutional doctrine is in play and ultimately on what constitutional value is at stake[111].
The Supreme Court of Canada has emphasised the importance of selecting the appropriate level of generality at which to describe a legislative purpose in the context of determining whether a law is "demonstrably justified in a free and democratic society" within the meaning of the Canadian Charter of Rights and Freedoms. In R v Moriarity[112], Cromwell J said:

Traditionally, an analytical distinction has been drawn between a legislative purpose that is "penal or punitive" and a legislative purpose that is no more than "protective" in the context of determining whether a law infringes the doctrine of separation of judicial power by conferring on a decision-maker other than a court a power to detain - or, more broadly, a power to constrain the freedom of action or to revoke or suspend the statutory status of - a person found to have contravened a statutory norm. On the one hand, a punitive purpose will be incompatible with the doctrine. On the other hand, a protective purpose may be compatible with the doctrine[113]. The distinction alone cannot be determinative of the ultimate constitutional inquiry as a law with a protective purpose may still pursue that purpose in a manner incompatible with the doctrine[114].
The distinction between a punitive purpose and a protective purpose has been said to be "elusive"[115] in the context of examining the effect of an exercise of power on a person who is its object. The distinction nevertheless remains analytically useful in the context of characterising the power as judicial or non-judicial, as long as the notion of what amounts to a protective purpose is kept within bounds which make the distinction meaningful.
Long recognised as protective in a constitutionally meaningful sense has been the purpose of upholding standards of integrity and competence amongst professionals and others who engage in activities involving elements of public trust[116]. That protective purpose has accordingly been recognised to have the potential to justify conferral of a power to revoke or suspend a statutory status of a person found to have contravened a statutory norm on a decision-maker other than a court. When undertaken as an incident of a legislative scheme designed to uphold such standards, "it is not readily to be assumed that disciplinary action, however much it may hurt the individual concerned, is personal and retributive rather than corporate and self-respecting"[117].
By parity of reasoning, when conferred on a decision-maker other than a court as an incident of a licensing regime designed to ensure that the content of radio or television broadcasting respects community standards[118], a power to revoke or suspend a broadcasting licence where a broadcast is shown to have fallen short of those standards can meaningfully be characterised as having the purpose of protecting the Australian community. Accordingly, a decision-maker responsible for administering a licensing regime of that nature does not exercise the exclusively judicial power of adjudging and punishing criminal guilt merely by making its own inquiry and forming its own opinion that a licensee committed a criminal offence in the course of determining whether that licensee has breached a condition of its licence[119].
The attempt by the defendants to analogise from a purpose of upholding standards to be expected of those who by choice engage in a profession or in an activity involving an element of public trust, or in radio or television broadcasting under statutory licence, to a purpose of upholding standards to be expected of all Australian citizens in virtue of them being Australian citizens must be rejected. It draws too long a bow. It stretches the concept of protection to breaking point. It deprives the distinction between "protective" and "punitive" of all utility.
In the context of determining whether a law infringes the doctrine of separation of judicial power, to say no more than that the purpose of a law is to protect the Australian community from an Australian citizen found to have contravened a statutory norm is to say nothing to indicate that the law has a purpose that is "protective" in a sense meaningfully distinct from a purpose that is "penal or punitive". That is because protection of the community from a citizen found to have contravened a statutory norm is a concept of such elasticity that it is not necessarily inconsistent with the imposition on that citizen of a criminal punishment following an adjudication of criminal guilt - a function which lies in the heartland of judicial power.
Indeed, "protection of society" has been identified as one of the "purposes of criminal punishment"[120]. In that regard, it has been said that "the protection of the community is one of the most important results that the criminal law is designed to secure"[121]. It has even been said that criminal law "exists for the protection of society" and that it is possible to discard the notion of punishment for punishment's sake and instead recognise that the imposition of criminal punishment pursues "the principles of rehabilitation, deterrence and, wherever necessary, the ultimate isolation from society of those individuals who have no capacity for the adjustments necessary to conform their conduct as active members of a free society to the requirements of the law"[122].
There is a notion of criminal punishment having protection of the community from future criminal conduct as its ultimate purpose which can be traced back to the Enlightenment. There is also a notion of criminal punishment encompassing protection of the community by removing the most recalcitrant of criminal contraveners from membership of the community altogether which is of even greater antiquity. In the late 18th century, Sir William Blackstone wrote[123]:

Identifying the purpose of a law is an exercise in attributing an objective intention to the outcome of a legislative process. The exercise is similar, although not identical, to the exercise involved in construing a law by attributing meaning to legislated text. The two are informed by the same textual and contextual considerations. The main difference between them is as follows.
To the extent that legislated text has operative legal effect, the operative legal effect inheres in the meaning of the text construed in the totality of its context. The text is in that sense, and for that reason, the beginning and the end of statutory construction[125].
To the extent that the legislated text includes a statement of purpose, that statement of purpose can "throw light on"[126] the mischief to redress of which the operative legislated text is directed. But the purpose does not inhere in the text. The text is in that sense, and for that reason, the beginning of the identification of legislative purpose but cannot be the end.
A legislature of limited powers "cannot arrogate a power to itself by attaching a label to a statute"[127] and cannot, merely by including a statement of purpose in legislated text[128], require a court to identify the purpose of a law as something that it is not. Not unknown in our constitutional history is for a law which purports to be designed to achieve a constitutionally permissible purpose to be found on close inspection "in truth" to pursue a constitutionally impermissible purpose[129].
That said, the constitutional relationship between the judiciary and the legislature is such that a statement of legislative purpose must be treated by a court as a solemn and presumptively accurate declaration of why a law is enacted. The declaration is made by the legislature to itself and to the world.
The legislatively declared purpose might well be elucidated with reference to other aspects of the text or context. It might need to be supplemented or qualified in order to explain some detail of the law. It might need to be translated to a level appropriate for constitutional analysis in a particular context. Absent strong reason for concluding that the stated purpose is not a true purpose, however, it must be accepted and respected.
When enacting the Australian Citizenship Amendment (Citizenship Cessation) Act 2020 (Cth) ("the 2020 Amending Act"), Parliament chose to explain the purpose of the whole of the subdivision within which s 36B is included. Parliament did so in s 36A. Translated to the level appropriate for analysis of the compatibility of s 36B with Ch III of the Constitution, the purpose declared in s 36A is properly characterised as one of denunciation and exclusion from formal membership of the Australian community of persons shown by certain conduct to be unwilling to maintain or incapable of maintaining allegiance to Australia. The nature of the conduct understood by the Parliament to be capable of showing that unwillingness or incapacity is elucidated by the operative provisions of the subdivision and is limited to criminal conduct found to have been engaged in by a person in the past. Thus the purpose of denunciation and exclusion from formal membership of the Australian community is solely on the basis of past criminal conduct. That purpose can only be characterised as "punitive".
The revised explanatory memorandum[130] for the Bill for the 2020 Amending Act contains nothing to cast the purpose of s 36B as declared by s 36A in a different light. Nor does the second reading speech[131].
The Bill for the 2020 Amending Act had its origin in a report to the Attorney-General in 2019 by the Independent National Security Legislation Monitor[132]. The parliamentary process which resulted in the Bill's enactment included an inquiry in 2019 and report in 2020 by the Parliamentary Joint Committee on Intelligence and Security ("the PJCIS")[133].
The defendants did not seek to draw on anything in either of those reports to support their submission that the purpose of s 36B is appropriately identified as the protection of the Australian community. Rather, they sought to draw on a submission made to the PJCIS in the course of its inquiry.
The submission was made by the Australian Security Intelligence Organisation ("ASIO")[134]. The thrust of that submission was that ASIO considered "citizenship cessation" to be "a legislative measure that works alongside a number of other tools to protect Australia and Australians from terrorism". The submission implied that ASIO saw those "other tools" as including prosecution for terrorism offences, which it said would sometimes result in "the better security outcome". The concept of "protection" which ASIO employed in its submission was therefore one that encompassed invocation of a judicial process by way of prosecution for an offence.
The language of "security" and "protection" in which ASIO cast its submission is explicable by reference to ASIO's statutory charter. The statutory functions of ASIO centrally include obtaining, correlating, evaluating and communicating intelligence relevant to "security"[135]. The definition of "security" relevantly includes "the protection of, and of the people of, the Commonwealth" from politically motivated violence[136].
A submission made by a responsible government agency to a parliamentary inquiry cannot be dismissed as beyond the scope of the material which might properly inform judicial identification of the purpose of a law. In the context of examining the compatibility of s 36B with Ch III of the Constitution, however, the ASIO submission to the PJCIS is of no analytical utility whatsoever. ASIO's frame of reference is such that even prosecution which results in the imposition of punishment by a court for a terrorism offence is regarded as being for the protection of the Australian community. That is not the frame of reference within which determining whether a statutory purpose is "protective" needs to occur in the context of the doctrine of separation of judicial power enshrined in Ch III of the Constitution. The concept of "protection" as employed in ASIO's submission to the inquiry therefore does not assist in identifying the purpose of s 36B in the context of the constitutional inquiry.

I agree with the answers proposed by Kiefel CJ, Keane and Gleeson JJ to the questions stated by the parties in the special case.
GORDON J. The plaintiff, Mr Alexander, conducts this litigation through a litigation guardian because his family and lawyers have not been able to contact him since 15 July 2021, shortly after he told them that he was being transferred to the Branch 235 prison in Damascus, Syria, operated by Syrian intelligence.
I gratefully adopt the description of Mr Alexander's plight, the Australian Government's decisions about Mr Alexander, the nature of the proceeding in this Court and the relevant provisions of Subdiv C of Div 3 of Pt 2 of the Australian Citizenship Act 2007 (Cth) ("the Citizenship Act") set out in the reasons of Kiefel CJ, Keane and Gleeson JJ.
Section 36B of the Citizenship Act confers a power on the first defendant, the Minister for Home Affairs ("the Minister"), to make a citizenship cessation determination if satisfied that: a person has engaged in specified conduct (relevantly identified by reference to the physical elements of certain terrorism‑related offences); the conduct demonstrates that the person has repudiated their allegiance to Australia; it would be contrary to the public interest for the person to remain an Australian citizen; and the person would not become a person who is not a national or citizen of any country.
On 2 July 2021, the Minister determined that Mr Alexander "ceases to be an Australian citizen" ("the Cessation Determination"). The Cessation Determination recorded that the Minister was satisfied: "that [Mr] Alexander ... has engaged in conduct specified in [s] 36B(5) of the [Citizenship] Act, namely engaging in foreign incursion, while outside Australia"; "that the conduct of [Mr] Alexander demonstrates that he has repudiated his allegiance to Australia"; "that it would be contrary to the public interest for [Mr] Alexander to remain an Australian citizen, having had regard to the matters specified in [s] 36E(2)"; and that Mr Alexander "would not, through the making of the determination, become a person who is not a national or citizen of any country" (emphasis in original).
Mr Alexander challenges the constitutional validity of s 36B on a number of grounds. These reasons address two grounds: (1) that s 36B is not supported by s 51(xix) of the Constitution, the "naturalization and aliens" power[137]; and (2) that s 36B reposes in the Minister the exclusively judicial function of punishing criminal guilt. Mr Alexander's challenge on the second ground should be upheld. It is, therefore, neither necessary nor appropriate[138] to determine whether s 36B is supported by the "naturalization and aliens" power or any of the other grounds raised by Mr Alexander[139]. But, given that other members of the Court do decide the question of legislative power, it is necessary to make some brief observations about the "naturalization and aliens" power.

By contrast, the "naturalization and aliens" power (s 51(xix)) and the immigration power (s 51(xxvii)) support legislation transforming aliens into non‑aliens, including by grant of statutory citizenship[152]. An aspect of the "naturalization and aliens" power is a power to determine how aliens lose the status of alienage, whether absolutely or upon conditions and, if the latter, on what conditions[153]. That aspect of the power reflects that it is a well‑recognised attribute of sovereignty that every nation state is entitled to decide what aliens shall or shall not become members of its community[154]. As a general proposition, persons who have been naturalised or otherwise admitted to membership of the Australian community cannot subsequently be treated as or converted into "aliens" by statute supported by the aliens power because the aliens power is spent once the person is naturalised or otherwise admitted to membership of the community. But, again, that is not without exception.
Persons who have been naturalised or otherwise admitted to membership of the Australian community, like persons who could not possibly answer the description of "aliens" in the ordinary understanding of the word, may lose their status of non‑alienage pursuant to legislation supported by the "naturalization and aliens" power where there are changes in sovereign identity or territory[155] or where the person has renounced their allegiance to Australia[156], expressly or impliedly, by engaging in specified conduct. Again, that is subject to potential issues regarding statelessness.
As will be apparent, to the extent that an impugned law addresses one or both of those exceptions, it is unnecessary to determine if a particular person is one who could not possibly answer the description of an "alien" in the ordinary understanding of the word or if they are a person who has been naturalised or otherwise admitted to membership of the Australian community. Whatever their status, s 51(xix) provides support for a law which is addressed to one or both of those situations.
The exceptions identified above may not be the only circumstances in which Parliament may denaturalise a person or otherwise withdraw a person's membership of the Australian community. One possible example is sufficient to illustrate the point. If a person breaches a condition validly imposed upon the grant of membership of the community[157], then, absent some other reason, it would be open to Parliament to make a law permitting withdrawal of that person's membership of the community for breach of the condition.
Other questions which do not require resolution in this proceeding may arise, including, first, whether conditions imposed on a person's entry into the community can be retrospectively changed to denaturalise the person or withdraw their membership of the community and thereby convert that person into an alien[158] and, second, whether a point can ever be reached, regardless of the conditions imposed on entry into the Australian community, where a person has become so connected to the Australian body politic that the connection cannot unilaterally be taken away by Parliament by converting the person into an alien.
As to the first matter, as Gaudron J stated in Chu Kheng Lim v Minister for Immigration, Local Government and Ethnic Affairs[159], s 51(xix) does not support laws "providing for denaturalization in the absence of some failure to observe the requirements associated with naturalization or in the absence of some relevant change in the relationship of the person or persons concerned with the community constituting the body politic". While that recognises the possibility that a person might be converted into an alien as a result of changes in sovereign identity or territory, renunciation of allegiance, or breach of conditions validly imposed upon the grant of membership of the community, it excludes the possibility that, absent such circumstances, Parliament could retrospectively impose conditions to denaturalise a person or withdraw their membership of the community. Gaudron J further relevantly observed in Re Patterson; Ex parte Taylor[160] that, "[a]bsent any [relevant] change, [a] law could not be classified as a law with respect to naturalisation or aliens, for that power is wholly concerned with the relationship of individuals to the Australian community".
As to the second matter - whether a point can ever be reached where a person is so connected to the Australian community that the connection cannot unilaterally be taken away by Parliament - it is enough, in this case, to make the following points. First, these issues were not considered or decided in either Singh v The Commonwealth[161] or Koroitamana v The Commonwealth[162]. The facts in neither case[163] provided a sufficient foundation for arguments of that kind. Second, as cases such as Sue v Hill[164] and Shaw v Minister for Immigration and Multicultural Affairs[165] show, the constitutional term "aliens" may have different application as national and international circumstances change[166]. It may be that the changes in national and international circumstances since Pochi v Macphee[167] was decided 40 years ago would mean that facts of the kind considered in Pochi could be said to call for some different answer today. That is not this case and, if argument of that kind were to be made, it would need a proper factual foundation.

Insofar as the defendants' submission that there is no distinction between natural-born and naturalised citizens is contrary to the preceding analysis, it should be rejected. The submission is not supported by the passage in Re Canavan[169] relied upon by the defendants.
In Re Canavan[170], the Court was addressing Deane J's reasoning in Sykes v Cleary[171], where his Honour had expressed the view that the second limb of s 44(i) of the Constitution was subject to a qualifying element, which "extends not only to the acquisition of the disqualifying relationship by a person who is already an Australian citizen but also to the retention of that relationship by a person who has subsequently become an Australian citizen" (ie, a naturalised Australian citizen). The Court in Re Canavan[172] held that the approach taken by Deane J drew no support from the text and structure of s 44(i).
It was in that context that the Court said that, "[i]n addition, the approach of Deane J places naturalised Australian citizens in a position of disadvantage relative to natural-born Australian citizens"[173]. The Court emphasised that the reasons of Mason CJ, Toohey and McHugh JJ, Brennan J and Dawson J respectively in Sykes v Cleary[174] did not draw any distinction between natural‑born Australian citizens and naturalised Australian citizens in terms of the application of s 44(i)[175]. The Court also noted that s 34 of the Constitution, unlike s 44(i), did draw a distinction between natural‑born and naturalised Australians for the purpose of qualifying to be a candidate for election[176].
No less significantly, the Court said that the absence from the text of s 44(i) of any distinction between natural-born and naturalised Australians "cannot be attributed to inadvertence on the part of the framers, both because the concept of citizenship by descent was commonplace at the time of federation, and because of the express provision in s 34"[177].
Four points may be made. First, the Court's observations were concerned with a different provision in the Constitution, s 44(i), which is not a head of power. Second, s 51(xix) in its terms refers to "naturalization". Third, a basic distinction between naturalised citizens and persons who could not possibly answer the description of "aliens" in the ordinary understanding of the word is that all persons who are naturalised were once aliens. As has been explained, it is well established that it is an attribute of sovereignty that every nation state is entitled to decide what aliens shall or shall not become members of its community[178] and, by a law with respect to "naturalization and aliens", the Parliament can remove the status of "alienage" absolutely or subject to conditions[179]. And breach of conditions validly imposed at the time a person became naturalised or was otherwise admitted to membership of the Australian community may result in denaturalisation or withdrawing that person's membership of the community. Fourth, and relatedly, it may be accepted that once a person is naturalised or otherwise admitted to membership of the Australian community (subject to any validly imposed conditions) they are in the same position as persons who could not possibly answer the description of "aliens" in the ordinary understanding of the word for the purposes of s 44(i), but that does not say anything about the "naturalization and aliens" power in s 51(xix).

In that regard it is sufficient for present purposes to refer to the first jurisdictional fact[186] conditioning the exercise of power to make a citizenship cessation determination under s 36B(1), namely that the Minister is satisfied that a person has engaged in conduct specified in s 36B(5)[187]. The conduct specified in s 36B(5) includes, among other things, "engaging in international terrorist activities using explosive or lethal devices"[188], "engaging in a terrorist act"[189], "engaging in foreign incursions and recruitment"[190], "fighting for, or being in the service of, a declared terrorist organisation"[191], and "serving in the armed forces of a country at war with Australia"[192]. The words and expressions used in s 36B(5)(a)‑(h) have the same meanings as they do in specified offence provisions of the Criminal Code (Cth), but this does not include the fault elements that apply to those offences[193].
It may be accepted that to the extent that s 36B(1)(a) covers the "paradigm case of implicit renunciation" of allegiance by "spying or fighting" for an enemy state declared to be at war with Australia, and the closely related category of conduct involving service in the armed forces of a declared terrorist organisation[194] (namely, the conduct of persons who could be described as "foreign fighters"[195]), s 36B is within the scope of the aliens power. Indeed, Australian laws have long provided that persons who fight in a foreign army at war with Australia or assist Australia's enemies in other ways may be denaturalised or have their citizenship revoked[196]. And Australia is not unusual in having enacted laws of this kind. Provisions depriving persons of citizenship for service in a foreign army have long existed in Canada[197], France[198], Germany[199], Italy[200], the Netherlands[201] and the United States[202].
On the other hand, again having regard only to the conduct criterion in s 36B(1)(a), to the extent that s 36B captures conduct beyond serving in the armed forces of a country at war with Australia and conduct of foreign fighters, it might exceed the scope of the aliens power.
It is unnecessary to address any other or additional basis on which s 36B is said to be supported by s 51(xix) (namely, that the Minister must be satisfied that the person's conduct demonstrates that they have repudiated their allegiance to Australia[203] and that the person is a dual citizen[204]). While accepting that s 51(xix) supports s 36B at least insofar as it is directed at conduct which plainly constitutes renunciation of allegiance, namely, fighting for an enemy state at war with Australia and conduct of foreign fighters, it is unnecessary to determine whether s 36B is supported by s 51(xix) in all of its operations in circumstances where the law is, in any event, wholly invalid[205].

Section 36B is invalid in its entirety because it is contrary to Ch III of the Constitution. It confers on the Minister the power to impose a sanction upon a person (involuntary cessation of citizenship) - a punishment - for that person engaging in past conduct of a kind identified as warranting the condemnation of the Australian community.
The principles are well established. The adjudgment and punishment of criminal guilt is an exclusively judicial function[206]. The Executive cannot "itself exercise judicial power and act as prosecutor and judge to punish breach of law by executive fiat or decree"[207]. The jurisprudence of this Court, to date, has been concerned foremost with executive detention, but the categories of punishment are not closed[208]. And that has to be so. The concern of Ch III is with substance, not form[209].
Section 36B does not require any person to be detained in custody. As such, Mr Alexander does not have the assistance of any "default characterisation"[210] of s 36B as being penal or punitive. The question then must be whether the involuntary cessation of citizenship effected by s 36B is a form of "punishment" of the requisite kind, that is, punishment that is penal or punitive in character. Critically, that requires considering whether, in the context of s 36B, involuntary cessation of citizenship is a measure which, "by reason of [its] nature or because of historical considerations"[211], should be characterised as penal or punitive and, therefore, exclusively judicial in character. As Mr Alexander submits, the fact that denationalisation is not a "punishment" for committing a crime in any Australian statute book is not determinative; nor are capital punishment and forms of corporal punishment now forms of punishment in any Australian State or Territory, yet there can be no doubt that they are punitive. And whether s 36B has the character of a law conferring a power to punish is a question of construction[212].
In Re Woolley; Ex parte Applicants M276/2003[213], in the context of considering executive detention, Gleeson CJ pointed out that not "all hardship or distress inflicted upon a citizen by the State constitutes a form of punishment, although colloquially that is how it may sometimes be described". His Honour went on to explain[214]:

Consistent with that purpose, in substance, s 36B authorises the Minister to impose a sanction upon a person (involuntary cessation of citizenship) for engaging in conduct of a kind identified as warranting the condemnation of the Australian community. The only point at which the protection of the Australian community is taken into account is for the purposes of assessing the third criterion in s 36B(1), namely whether it would be contrary to the public interest for the person to remain an Australian citizen[217]. The matters that the Minister must have regard to in considering the public interest for the purposes of deciding whether to make a determination under s 36B(1) are listed in s 36E(2). Only one of the matters listed - "the degree of threat posed by the person to the Australian community"[218] - concerns protection of the Australian community. Section 36B stands very far removed from the kinds of provisions with protective purposes considered in earlier cases[219].
The character of citizenship cessation for the purposes of s 36B must also be considered in light of the Minister's role in adjudicating on whether a person has engaged in conduct that constitutes the physical element of identified offences[220]. Two matters are significant. First, s 36B operates with respect to "identified and articulated wrongdoing"[221]. Second, the cessation of citizenship is "a consequential step" after the Minister's adjudication that the person has engaged in "past acts" which, if accompanied by specified fault elements, would involve criminal guilt[222]. Put differently, the power to make a citizenship cessation determination under s 36B is specifically linked with conduct "for which [it] might be regarded as punishment"[223].
And an exercise of power under s 36B does not simply involve "inflicting ... involuntary hardship or detriment by the State"[224]. The consequences of an executive citizenship cessation determination under s 36B are loss of fundamental rights of citizenship with immediate effect[225], and permanently[226]. Those consequences are significant. If the person is overseas, they will be unable to return to Australia, unless granted a visa. If the person is in Australia they will immediately become an "unlawful non-citizen" who must be taken into immigration detention and is liable to be removed from Australia as soon as reasonably practicable[227].

In 1597, the English Parliament enacted a law that provided that convicted dangerous rogues be "banyshed out of this Realme and all other the Domynions thereof"[232]. From that time until 1864, "Parliament at frequent intervals passed new statutes reaffirming the use of this punishment"[233]. In 1616 in Dr Hussey v Moor[234], the Court of King's Bench identified the existence of three kinds of punishment: "pecuniary, corporal and exile". In respect of a statute imposing all three, it was held that "the same gives damages, corporal punishment, and exile, to lose his country, and if this be not a penal law, I do not know what law is penal" (emphasis added).
In the 17th edition of Blackstone's Commentaries on the Laws of England, published in 1830, in a chapter on "judgement and its consequences", in the context of considering what he described as "the next stage of criminal prosecution, after trial and conviction are past", Blackstone said that the court must pronounce the judgment which the law has annexed to the crime[235]. Blackstone explained that some punishments are capital, which extend to the life of the offender, and "[s]ome punishments consist in exile or banishment, by abjuration of the realm, or transportation: others in loss of liberty, by perpetual or temporary imprisonment"[236] (emphasis added). Similarly, in 1890, Craies observed that under English law "[t]he purposes for which a subject could conceivably be required to leave the realm [fell] into two main classes - public service, and punishment for crime"[237] (emphasis added).
In 1933, Plucknett distinguished outlawry (which involved "withdrawal by civil society of all legal rights and protection from one of its offending members") from "less serious penalties, such as exile, which was generally a voluntary withdrawal not resulting directly in loss of property or civil rights [and] banishment, which was similar save that it was compulsory"[238] (emphasis added).
Denationalisation, as a form of punishment, was also directly addressed by the Supreme Court of the United States in 1958 in Trop v Dulles[239]. Warren CJ observed of denationalisation that[240]:

Mr Alexander is an Australian‑born citizen who is in a prison in Damascus operated by Syrian intelligence. In May 2021, the President of Syria decreed a general amnesty law pardoning perpetrators of a number of violations, misdemeanours, and felonies. Mr Alexander informed his family in June 2021 that he had been pardoned for his convictions under the Syrian Penal Code. Mr Alexander claims that, according to his Syrian lawyer, a reason that he remains in detention is that the Minister for Home Affairs has declared that he is no longer an Australian citizen. In his application for constitutional writs, Mr Alexander alleges that he is in danger of torture, serious bodily harm, or death.
Senior counsel for Mr Alexander politely requested that this Court consider adopting the approach of pronouncing orders before reasons in order to facilitate expedition of the result of this case in light of these "parlous circumstances" of Mr Alexander. I would have readily acceded to that request. The justification for the request was significantly more compelling than many, perhaps any, other instance in which this Court has recently, and properly, taken such an approach[246]. There was no suggestion at the oral hearing that any circumstance pointed against that proposed course. In any event, these reasons, like those of the other members of this Court, were prepared very shortly after the hearing in order to facilitate an expeditious delivery of the orders.
In these reasons, I gratefully adopt the facts, background, and statutory scheme comprehensively set out in the reasons of Steward J, and also in the reasons of Kiefel CJ, Keane and Gleeson JJ. It suffices for these reasons simply to reiterate that Mr Alexander was born in Australia in 1986 and became an Australian citizen by birth. His parents were permanent residents of the Commonwealth of Australia at the time of his birth. His mother became an Australian citizen before Mr Alexander was two years old. Like millions of Australians, Mr Alexander was born a dual citizen due to the citizenship of his parents. On 2 July 2021, the Minister made a determination under s 36B of the Australian Citizenship Act 2007 (Cth) that Mr Alexander ceased to be an Australian citizen.
This special case essentially asks whether Mr Alexander was always an alien within the meaning of the aliens power in s 51(xix) of the Constitution or, if not, whether Commonwealth legislation validly permitted him to be stripped of his citizenship for other reasons. Section 36B of the Australian Citizenship Act permitted the Minister to make a determination that Mr Alexander ceased to be an Australian citizen if the Minister was satisfied that: (i) Mr Alexander engaged in specified conduct while outside Australia; (ii) the conduct demonstrates that Mr Alexander has repudiated his allegiance to Australia; (iii) it would be contrary to the public interest for Mr Alexander to remain an Australian citizen; and (iv) Mr Alexander would not, if the Minister were to make the determination, become a person who is not a national or citizen of any country. This special case challenges the constitutional validity of s 36B.
There are four questions raised by this special case[247]. First, is s 36B of the Australian Citizenship Act supported by a head of Commonwealth legislative power? Secondly and thirdly, is s 36B inconsistent with two asserted implied limitations upon the Commonwealth legislative power under s 51(xix) of the Constitution? Fourthly, does s 36B repose in the Minister "the exclusively judicial function of punishing criminal guilt"?
As to the first question, the only head of power relied upon by the defendants to support s 36B is the power over "naturalization and aliens" in s 51(xix) of the Constitution. This raises the question of how the meaning of "alien" - a foreigner to the political community - is to be applied. On the approach of the defendants, all dual citizens fall within the aliens power. Therefore, there is power to pass a law such as s 36B of the Australian Citizenship Act simply because all the people to whom it applies are dual citizens. That would mean that, subject to any separate implied limits, the Commonwealth Parliament would have the power to strip persons like Mr Alexander of their citizenship solely because they are dual citizens. The defendants also argued that s 36B is a valid law because the Commonwealth has power in circumstances described as "repudiation of allegiance" to make non‑aliens into aliens.
The application of the essential meaning of "alien" that was urged by the defendants has the likely consequence that potentially half of the permanent population of Australia are aliens, being dual (or more) citizens, being born overseas, or having at least one parent who does not hold Australian citizenship. Almost by definition, something must have gone wrong in the application by this Court of the meaning of the Constitution for it to be concluded that the Commonwealth Parliament has power to legislate on the premise that potentially half of the people of the Commonwealth of Australia are foreigners to the political community of the Commonwealth of Australia.
Nevertheless, the defendants' approach was only an incremental extension of the present state of the law concerning the application of the aliens power. That approach is the result of the compounding effect of a series of decisions of this Court. Those decisions have seen an imperial march of the application of the aliens power, extending it far beyond any ordinary understanding, capturing more and more members of the permanent population of the Commonwealth of Australia. At some point it will become necessary to confront the correctness of those decisions rather than tip‑toeing around them, carefully confining them by tiny exceptions, or restricting their scope by recognising implied constitutional constraints such as those raised by the second and third questions in this special case. It is not necessary to do so in this case because none of the decisions was challenged.
The compounding effect of the decisions of this Court began in 1982, when this Court first held that persons who had been unconditionally absorbed into the Australian political community were still within the reach of the aliens power. From that premise, and case by case, the application of the essential meaning of "alien" - a foreigner to the Australian political community - was extended further and further to apply to persons who had less and less "foreign" connection. It might seem like only another small, incremental step to conclude that Mr Alexander is a foreigner to the Australian political community, despite his birth in Australia to two permanent members of the Australian body politic. But, with an appreciation that the decisions of this Court may have already stretched the application of alien beyond breaking point, that is a step that should not now be taken.
Although s 36B cannot validly apply to persons simply on the basis that they are dual citizens, and would not have applied to Mr Alexander at the time of his birth, the aliens power does permit the Commonwealth Parliament to legislate, as it did in s 36B of the Australian Citizenship Act, in relation to non‑aliens who act in a manner that has been described as a repudiation of their allegiance to Australia. The aliens power permits the Commonwealth Parliament to legislate in relation to some people who were not aliens in extreme cases where circumstances or conduct are capable of making them into aliens. One such circumstance is where a person's conduct is so wrongful and extreme that it can be judged to be inconsistent with continuing membership of the political community. That is the effect of s 36B, so, subject to any other constitutional limits, s 36B would therefore be valid.
In light of the distorted state of present authority concerning the aliens power it would not be appropriate to consider the two implied limits upon the aliens power that were the subject of Mr Alexander's submissions unless it were necessary to do so. Those limits broadly concerned the effect of being a member of the political community of the Australian body politic. It is not necessary to consider those limits because I have concluded that s 36B imposes a punishment upon those people to whom it applies. As a Commonwealth law with the purpose of punishment by the Minister as a sanction for proscribed conduct, s 36B is invalid because it is contrary to the implied constitutional proscription on the exercise of federal judicial power by a body other than a Ch III court.

It has been suggested[248] that the aliens power resembles legislative powers conferred by the Constitution on the Commonwealth Parliament to make laws with respect to a legal status, such as bankruptcy[249], trade marks[250], and marriage[251], rather than resembling legislative powers conferred by the Constitution with respect to physical things, like lighthouses, lightships, beacons, and buoys[252]. There are grave difficulties with the creation of separate constitutional principles within s 51 according to those classes concerned with physical things and those concerned with legal status on the basis that the former "are fixed by external nature" and "cannot well be extended"[253].
All of the powers in s 51 are expressed by words which convey meaning, with the meaning anchored in its essence, at the appropriate level of generality, by the contemporary understanding at Federation. That meaning is ideational. It is not confined to categories of physical things or legal status. Indeed, numerous powers might even derive the essence of their meaning from both. For instance, fisheries in Australian waters beyond territorial limits[254] are concerned with both physical things and legal status. So are bills of exchange or promissory notes[255]. The custody and guardianship of infants[256] concerns both people and legal status, and so does "the influx of criminals"[257]. Further, just as the application of the essential meaning of words that describe a legal status can change, so too a power that appears limited to purely physical things, such as a lighthouse, lightship, beacon, or buoy, might arguably extend to things never contemplated in 1900 but which are within the same concept, fulfilling the same purpose, such as global positioning system software for seafarers.
Although there is no warrant for creating new and separate constitutional categories within s 51, the character of a s 51 power can still influence the interpretation of the power[258], particularly where the character reveals a purpose of the power. But one matter must be common in the interpretation of every power in s 51. It is an axiom of constitutional law in Australia that "[t]he validity of a law ... cannot be made to depend on the opinion of the law‑maker": "a stream cannot rise higher than its source"[259]. Hence, no power in s 51 of the Constitution, whether in relation to legal status or not, is with respect to a subject matter that is determined by the opinion of the Commonwealth Parliament. The Parliament is not empowered to make laws based solely on the criterion that, in its opinion, the law is with respect to a status of bankruptcy, trade marks, or marriage.
In the context of bankruptcy, the legislative power is ample but it extends only "to regulate all matters which fairly fall within that subject"[260]. The power is constrained by reference to the "essential feature ... that provision is made for the appropriation of the assets of the debtor and their equitable distribution amongst [their] creditors, and for the discharge of the debtor from future liability for [their] existing debts"[261].
In the context of trade marks, it has been emphasised that "[i]f the thing is not of itself within the meaning, an Act of Parliament cannot make it so"[262]. If the Parliament were to enact legislation dealing with a matter which did not have the "essential qualities"[263] or "common attributes"[264] of a trade mark, it would not be "in essence a species within the language of the legislative powers" and would "amount to an attempt to amend the Constitution by a process not sanctioned by the Charter"[265].
In relation to passing laws dealing with the personal relationships that are the consequences of the marriage power, it has been observed that, "[s]o far as they can be regulated by law without impairing the essence of marriage", laws about the consequences of marriage, such as cohabitation, would "properly be called laws with respect to marriage"[266]. The power "does not support a law which so regulates the incidents of marriage as to impair the essence of marriage"[267]. In other words, "[t]he term marriage bears its own limitations and Parliament cannot enlarge its meaning"[268]. An exercise of "constitutional interpretation of the marriage power would be an exercise in hopeless circularity if the Parliament could itself define the nature and incidents of marriage by laws enacted in purported pursuance of the power"[269].

In an apparently innocuous statement in the joint judgment in Chetcuti v The Commonwealth, four members of this Court[272] said that it was a "settled understanding" that "the aliens power encompasses both power to determine who is and who is not to have the legal status of an alien and power to attach consequences to that status". If read literally, that statement would be a radical new theory of interpretation of constitutional heads of power.
If the statement in Chetcuti were read literally and without qualification, it might support an assumption that a constitutional alien is no more than the antonym of a statutory citizen. If that were true, then s 51(xix) would confer an unconstrained power on the Parliament to choose its own criteria for citizenship and thereby determine who is an alien and attach consequences to that alienage. Applied to other powers, this reasoning would mean that the Parliament could make laws to divest the assets of Croesus among his creditors on the basis that the Parliament determined for itself the meaning of bankruptcy, irrespective of the essential features inherent in the constitutional meaning of bankruptcy. The Parliament could "define 'trade mark' as including a will, and enact that no will shall be valid unless registered as a trade mark"[273], contrary to "universal agreement in the laws of every part of the British Empire" at the time of Federation concerning "certain essentials founded in the origin and very nature of a trade mark"[274]. Or the Parliament could pass laws in relation to the merger of corporations, or forced, non‑consensual unions, on the basis of its own determination of what a marriage is, thus enlarging that meaning beyond its constitutional essence as "a consensual union formed between natural persons in accordance with legally prescribed requirements" and bearing certain characteristics[275].
The statement quoted above from the joint judgment in Chetcuti should not be read as rejecting a century of hornbook constitutional law. Rather, and consistently with the acknowledgement in the previous paragraph in Chetcuti that a law of the Parliament might need to be disapplied to the extent of "constitutional overreach" by treating "all non‑citizens as aliens"[276], the statement in Chetcuti should be understood as saying no more than that the Commonwealth Parliament has power to set the criteria for who will, and who will not, be a statutory alien and the consequences of that, provided always that the exercise of that power is within the boundaries of the constitutional concept of "alien". In oral submissions, the defendants quite correctly accepted that position, conceding that the aliens power "cannot be used to treat, as an alien, someone who cannot answer that description on the ordinary understanding of the word"[277].
The ordinary understanding of the word "alien" - its essential meaning - is simple and well‑established in this Court. At a reasonably high level of generality, which recognises the state of flux at lower levels of generality of the common law of alienage at the time of Federation[278], an alien is a foreigner or outsider to the political community of the Australian body politic[279]. The difficult question is how that ordinary understanding of "alien" is to be applied.
On the submission of the defendants, the application of alien extends to people who have any of the following characteristics, each of which involves some "foreign" element: (i) the person has dual citizenship; (ii) the person was not born in Australia; or (iii) at birth, the person had one or more parents who were not an Australian citizen. It is likely that these slight foreign connections describe more than half of the Australian population; the first criterion alone involves close to half of the Australian population and the second and third criteria together likely involve a similar proportion. On the defendants' submission, therefore, potentially half of the Australian population are aliens within the meaning of the Constitution and can therefore be treated in that way by legislation.
It is not to the point that it might be thought to be extremely unlikely that the Parliament would ever legislate to impose the consequences of alienage, potentially including deportation, upon half of Australia's population. The identification of the extreme reach of the power on the submissions of the defendants is not to propose an absurd or distorting possibility[280]. Rather, the extreme reach of the power, over more than half of the population of Australia, and the infinite range of possible laws over those persons, or groups of them, which would be within the scope of the power illustrate the difficulties with the proposed interpretation[281].
The submission of the defendants was, nevertheless, a carefully devised formulation of the application of the essential meaning of "alien" which respected a line of authority in this Court since 1982. The extreme effect of the submission is only an incremental extension of a series of problematic decisions in this Court. Those decisions have developed the law to a point where the question that is asked of s 51(xix) is no longer which people are aliens. The question that is now asked is usually couched in the euphemism of "the Pochi[282] limit to the aliens power". But that "limit" is not some outer extreme within which Parliament has free rein. Rather, it is an absolutely orthodox requirement that the aliens power be applied in accordance with its meaning. As the application of the aliens power has strayed further and further from its essential meaning, the question has become how to identify which categories or groups of people are not aliens. And as the groups of people who are not aliens have come to be treated as diminishingly smaller, the answer to that question has not been readily forthcoming.
This case is not the appropriate vehicle to consider the extent to which it is possible to unwind some, or all, of the arguable errors in the decisions of this Court. But, in order to address the submissions of the parties on the first issue in this special case, it is necessary to identify where potential missteps may have occurred in order to explain why the aliens power should not extend any further to dual citizens born in the same circumstances as Mr Alexander.

There is much to commend about the approach, prior to 1982, which assumed that a like application, and like limits, would apply to the power to deport permanent residents of Australia whether they were aliens or immigrants. That application, which involved an approach that had been used consistently for decades, asked whether a person had been unconditionally absorbed into the Australian community. There are three particularly powerful reasons in support of such an application.
First, a focus upon unconditional absorption into the Australian community is an application that is consistent with the ordinary and essential meaning of "alien" and with contemporary standards. Whatever might have been the prevailing application at the time of Federation or shortly afterwards[289], by contemporary social mores a person is not a foreigner or outsider to the Australian body politic once the person is unconditionally absorbed into the Australian community.
Secondly, a coherent constitutional design would apply the same rules for when a person can be excluded from a political community as it does for when a person can be expelled from that community. The power to deport, whether under the aliens power or the immigration power, has been consistently recognised to be "the complement" of the power to exclude[290]. Put negatively, it would be a curious constitutional design that would make it easier to be expelled from a community than to be admitted to the community. It would be bizarre if s 51(xix) and s 51(xxvii) were to be applied in a manner that recognised that at the very point a permanent resident was unconditionally absorbed into the Australian political community and ceased to be an immigrant, the person became liable to be expelled from the Australian political community for any reason and at any time.
Thirdly, this application of the meaning of the aliens power to facts aligns with the other aspect of s 51(xix), naturalisation, which is concerned with the formal legal recognition that a person has been absorbed into the Australian political community. As Williams J said in Australian Communist Party v The Commonwealth[291], s 51(xix) extends to a person who is "in fact and law an alien". Conversely, a person can become a member of the political community - a non‑alien - either as a matter of fact or as a matter of law.
As a matter mainly of fact, the person can become a member of the political community at birth by powerful ties to the community beyond mere physical presence. Those ties can include being born in the territory of the Australian community to a parent or parents who are permanent members of the community, or having a deep and historical connection with that territory. Also as a matter mainly of fact, a permanent resident can become a permanent member of the community when the person has been unconditionally absorbed into the community.
As a matter of law, a person can be unconditionally absorbed into the community. It was well recognised prior to Federation, and has been recognised ever since, that the Parliament has wide legislative powers to confer upon any person, or to empower the Executive to confer upon any person, formal legal membership of the political community. This power of the Commonwealth Parliament to decide, as a matter of law, who is to be formally naturalised is broad. In that respect, citizenship legislation is a central "norm from which a political community is determined"[292]. The membership might be absolute or, as in the case of a denizen[293], it might be limited. And, like the power over immigration, the membership might be subject to reasonable conditions. But this Court does not countenance an application of the Constitution that "places naturalised Australian citizens in a position of disadvantage relative to natural‑born Australian citizens"[294]. Subject to reasonable conditions that might be imposed on a person at the time of naturalisation in the same manner as reasonable conditions might be imposed on immigrants, it is difficult to see any justification for treating a power to legislate with respect to "naturalization and aliens" as permitting a person once naturalised to be treated any differently from a person who was never an alien.

In Pochi v Macphee[295], Mr Pochi was born in Italy to Italian parents. He emigrated to Australia in 1959, married an Australian woman and lived in Australia for 20 years. As Murphy J said[296], apart from lack of citizenship, Mr Pochi was "in every way an Australian". He had been absorbed into the Australian community with the consequence that he was no longer able to be deported under the immigration power in s 51(xxvii). Mr Pochi argued that the power to deport him in s 12 of the Migration Act 1958 (Cth) was invalid. That section empowered the Minister to deport an alien who had been convicted in Australia of an offence for which they were sentenced to a term of imprisonment of one year or longer. The Migration Act "absorb[ed] the existing Aliens Deportation Act [1948 (Cth)]"[297] but did not "seek greater power for the executive than exist[ed]" previously[298].
Mr Pochi's submission was extreme. He argued that the aliens power could not apply to any person who had been absorbed into the community[299]. On that view, a person who came to Australia as an alien, and was permitted to remain only for a limited period of years, could avoid deportation by becoming part of the community. This Court unanimously rejected that view. As Gibbs CJ said, it was "impossible to maintain"[300]. One obvious reason for that impossibility is that unconditional absorption can never occur whilst a person is in Australia on a conditional or temporary visa. The expectation of a person holding an unexpired, limited entry permit is only that they should be "allowed to stay for the permitted time"[301]. So too, the expectation of a person holding an entry permit subject to reasonable conditions is only that they should be allowed to stay so long as they comply with those conditions.
The submission that was not made in Pochi v Macphee, and the issue which therefore cannot be taken to have been decided[302], was that a permanent resident of Australia who had been fully and unconditionally integrated into the community was not an alien. Depending upon whether his residence in Australia had become unconditional or remained subject to a condition of non-commission of various crimes[303], that narrower submission might arguably have applied to Mr Pochi. But, since it was not raised, it was not necessary for the Court to consider it.
In his Honour's reasons, however, Gibbs CJ, with whom Mason and Wilson JJ agreed, spoke of the limits of the application of the aliens power that are dictated by the ordinary meaning of "alien" as a foreigner to the political community[304]:

Without doubt, Gibbs CJ was correct to identify that the constitutional word "aliens" must bear its ordinary meaning. It would have been an abdication of this Court's constitutional duty if the Court had concluded that the Parliament could expand its own power by statutory redefinition of a constitutional term. But, at least by the values and standards of today, Gibbs CJ's application of that impeccable reasoning would be flawed if it were taken (beyond the strict ratio decidendi) as accepting the proposition that a permanent resident of Australia, fully and unconditionally absorbed into the community over a lengthy period, remained an alien within s 51(xix) of the Constitution and vulnerable to deportation. Such people are not, in any modern and ordinary application of the meaning of "alien", foreigners to the Australian political community.
Even after Pochi v Macphee, the initial response of the Commonwealth Parliament was not to adopt an overly broad application of the aliens power that treated all permanent residents, even if fully and unconditionally integrated into the Australian community, as falling within the meaning of "alien" in s 51(xix). In 1983, s 10 of the Migration Amendment Act 1983 (Cth) amended the Migration Act to repeal and replace the separate powers to deport aliens and immigrants. In the second reading speech, the Minister recognised that discrimination between "permanent resident aliens" and "other immigrants" was "totally unacceptable to the Government"[305]. The legislation generally prevented deportation of any alien who was a permanent resident, like any immigrant, if the person had been in Australia as a permanent resident for 10 years. The Minister added that "the overwhelming majority of non-citizens who have settled in Australia and have contributed to the development of this country have a right to expect, after 10 years of lawful residence, that they will not be expelled"[306].
However, after the statutory 10 year period was abandoned, an overly broad application of the aliens power was adopted in decisions of this Court that, described politely, would strike an ordinary person as very curious. A majority of this Court reasoned in Shaw v Minister for Immigration and Multicultural Affairs[307] that the prosecutor in Re Patterson; Ex parte Taylor[308], Mr Taylor, was an alien due to his British citizenship despite having been a permanent resident in Australia for more than 30 years from the age of six and on State and federal electoral rolls since the age of 18. This Court concluded in Falzon v Minister for Immigration and Border Protection[309] that Mr Falzon was an alien due to his Maltese citizenship, despite his permanent residence in Australia for 61 years after emigrating from Malta at the age of three. This Court also concluded in Chetcuti v The Commonwealth[310] that Mr Chetcuti was an alien despite his permanent residence in Australia for 69 years, during which he was a voter in local, State and federal elections and a registrant for military service, having arrived from Malta at the age of two as a British subject.
In the latter two of the cases above, and in the absence of any challenge to the reasoning in Pochi v Macphee[311] or any argument about the scope of its ratio decidendi described above, I supported those conclusions. But, since there was no suggestion that the permanent Australian residence of Mr Taylor, Mr Falzon, or Mr Chetcuti remained conditional, it is very hard to see how those conclusions can be supported by any ordinary application, with regard to today's morals and standards, of the essential meaning of "alien" as a foreigner or outsider to the Australian political community.
Any degeneration into further incoherence in the application of the aliens power could be arrested in this case, even whilst preserving the curious results in Pochi v Macphee and like cases. That arrest could occur by recognising that the application of the essential meaning of "alien" does not extend to persons who are born into the Australian community, such as by being born in Australia to a permanent member or members of the Australian community. That possibility was left open in argument by the Commonwealth in Singh v The Commonwealth[312].
In Singh v The Commonwealth[313], Gummow, Hayne and Heydon JJ held that Ms Singh was an alien within the meaning of s 51(xix) because, despite being born in Australia, she owed "obligations to a sovereign power other than [the Commonwealth of Australia]". On their Honours' approach, Ms Singh's dual nationality was sufficient to make her an alien. But that was not a majority approach. Gleeson CJ held that Ms Singh was an alien by focusing not merely upon her dual nationality but also upon her parentage: she was "a citizen of a foreign state [and] the child of foreign citizens"[314]. Kirby J held that Ms Singh was an alien because she was only a "temporary member of the community" with two foreign national parents[315]. At the time of her birth, her parents were in Australia awaiting the review of the refusal of their application for a protection visa[316]. McHugh J and Callinan J, both dissenting, held that Ms Singh was not an alien because she was born in Australia and remained a member of the Australian community[317].
The conclusion of the majority in Singh was extended in Koroitamana v The Commonwealth[318]. In that case, this Court held that two children were aliens even though they were born in Australia, had lived continuously in Australia since their births in 1998 and 2000, had three siblings all of whom were Australian citizens, and did not have citizenship of any other country. Gummow, Hayne and Crennan JJ said that the statelessness of the children at birth was sufficient to make them aliens[319]. Importantly, however, their Honours emphasised that the statelessness of the children at the time of their birth arose in circumstances in which: (i) their parents were citizens of the Republic of the Fiji Islands and had not registered the children for citizenship, and (ii) their parents were not Australian citizens or permanent residents[320].
Case by case, this Court has moved the application of the essential constitutional meaning of "alien" further and further from ordinary conceptions. Until the above authorities are revisited, this Court should take great care not to extend those authorities any further lest, as would be the consequence of the defendants' submissions, potentially half of the permanent population of Australia become constitutional aliens. The word "alien" would then be so devoid of meaning in the Constitution that it would make more sense to ask which Australians are not aliens. Even now, that question is difficult to answer.
Although the defendants' submissions might support such a conclusion, this Court has not yet recognised that a person born in Australia to parents of whom at least one is a permanent member of the Australian community can be a constitutional alien. At the time of Federation, such a conclusion was regarded as one which did not permit any difference of opinion. Writing in 1880, in a passage from his celebrated book, repeated in an edition published shortly before Federation[321], W E Hall said[322]:

In this part of the argument on this special case, there was confusion between constitutional concepts and statutory concepts. The constitutional concept of "alien" must be kept separate from the statutory concept of citizen. At the statutory level concerning citizens, the Parliament can make laws in relation to citizenship in reliance upon powers that include naturalisation and aliens, immigration, and the implied nationhood power[324]. The power of the Parliament to make a law also entails the power of the Parliament to repeal the law[325]. It is open for the Parliament to repeal any valid statutory enactment as to the criteria for statutory citizenship.
Constitutional considerations operate at a different level. They constrain both the extent to which the Parliament can make laws and the scope of the application of those laws. Section 51(xix) and the implied nationhood power confer broad powers upon the Parliament to enact laws conferring citizenship on constitutional aliens and non‑aliens alike. But, subject to limited exceptions discussed below, neither s 51(xix) nor the implied nationhood power permits persons to be treated as aliens if they are not aliens under the Constitution, at least where they were absorbed into the political community from birth or they were naturalised. As Gordon J expresses the point[326], once a person is naturalised according to whatever might be the requirements of a Commonwealth law made under s 51(xix), the legislative power over naturalisation is "spent" in relation to that person, subject to any reasonable conditions that are imposed. The naturalisation law might be amended or repealed but a person who has been naturalised is generally beyond the scope of the power.
There are exceptions. As the reasons of Gordon J demonstrate, it cannot be denied that s 51(xix) supports laws that regulate some circumstances in which a person can cease to be a member of the political community of the Australian body politic[327]. Such circumstances include: a change in sovereign identity or territory; breach by a naturalised member of the political community of a reasonable condition upon membership; and express or implied renunciation of membership of that political community. Each of these circumstances is a natural cause of the cessation of membership of a political community: a change in the community itself; a failure of an express, and reasonable, condition subsequent to membership of the community; or voluntary abandonment of membership of the community.
The premise of s 36B of the Australian Citizenship Act is that a further circumstance exists where, by s 36B(1)(b), a person has engaged in conduct which "demonstrates that the person has repudiated their allegiance to Australia". It is implicit in s 36B that the section will apply irrespective of whether the person's conduct permits an inference that the person wished to renounce their membership of the political community. In this respect, as Steward J explains[328], the premise of s 36B aligns with the reasoning of Frankfurter J, who said, in delivering the opinion of the Court in Perez v Brownell[329], that a person can lose their citizenship without any "intention of endangering [it] or of renouncing [their] allegiance".
So, what is the meaning of the objective concept of repudiation of allegiance in s 36B? In a number of decisions of this Court[330], most recently that of Kiefel CJ, Gageler, Keane and Gleeson JJ in Chetcuti v The Commonwealth[331], members of this Court have quoted with approval the observation of Professor Parry[332] that "[t]he concept of allegiance, which had been the foundation of the status of a subject, was not imported into the rules governing local citizenship but was altogether swept away, together with all other rules of the common law respecting nationality". The statutory reintroduction of the concept in s 36B requires explanation.
The terms in which Steward J explains the statutory concept of allegiance in s 36B, with which I agree, associate that concept with membership of the community of the Australian body politic[333]. Whatever might have been its previous force as a concept of law, allegiance remains in use here as a metaphor to describe the association or belonging that a person has as a member of a community which brings additional civic rights and duties. Section 36A confirms that the concept of allegiance, and the repudiation of it, is used in that way in s 36B: "the Parliament recognises that Australian citizenship is a common bond, involving reciprocal rights and obligations, and that citizens may, through certain conduct incompatible with the shared values of the Australian community, demonstrate that they have severed that bond and repudiated their allegiance to Australia".
Renunciation of allegiance therefore arises, as Steward J explains[334], irrespective of any subjective intention to sever a bond of membership, "from actions or steps that are indelibly inconsistent with ... membership of [the Australian political] community". In other words, although it is inherent in a political community's legal regulation of its membership that a person can commit wrongdoing, even extremely serious wrongdoing, whilst remaining a member of the political community, there will come a point at which the person's wrongdoing is so extreme that it can be judged to be inconsistent with continuing membership of the political community. I therefore agree with Steward J[335] that the limited class of conduct which might justify loss of citizenship "might include actions which seek to destroy or gravely harm the fundamental and basal features of the nation guarded by its Constitution, such as representative democracy and the rule of law, and actions directed at overthrowing state institutions where such conduct amounts to a clear rejection of allegiance to Australia. Terrorist attacks might also be included."
On its proper interpretation, s 36B of the Australian Citizenship Act is consistent with this reasoning. The objective conduct caught by ss 36B(1)(a) and 36B(5), involving matters related to terrorism, foreign incursions, and service in the armed forces of a country at war with Australia, provides a baseline for the extreme nature of the conduct required to establish a repudiation of allegiance, albeit divorced from any mental element that would render that conduct an offence. Plainly some objective conduct that is picked up by s 36B(1)(a) will come nowhere near the extreme, wrongful acts required to satisfy s 36B(1)(b). Mr Alexander even cited examples of such non‑wrongful conduct, including a pharmacist who innocently keeps poisons. But the validity of s 36B hinges upon the extreme wrongdoing that is required by, and inherent in, the notion of repudiation of allegiance to Australia to be determined by the Minister.

There can sometimes be a very fine line between (i) punitive laws, which have as one of their purposes sanctioning proscribed conduct by making it subject to harsh consequences, and (ii) laws which use certain conduct merely as a factum which informs a decision to impose harsh consequences for separate purposes concerning the public interest. The category that a law falls into will depend upon the identified purposes of the law.
The assessment of the purpose of a law involves "ordinary processes of interpretation, including considering the meanings of statutory words in the provision, meanings of other provisions in the statute, the historical background to the provision, and any apparent social objective"[343]. An express statement of statutory purpose will almost always be relevant to that exercise, all the more so where the statement of purpose concerns the relevant provision rather than the entire Act, but the question for a court will always be the "characterisation of the purpose of a provision at the appropriate level of generality"[344].
An example of a law that imposes harsh consequences, but not for the purpose of sanctioning proscribed conduct and thus not for the purposes of punishment, is a law that permits the termination by the Commonwealth of a lease over premises which have been used for an unlawful purpose[345]. The purpose of the harsh consequence of termination is not to punish the unlawful conduct. It is to protect the interests of the lessor. Another example is the disqualification of a person from managing a corporation where that disqualification is "for the purpose of maintaining professional standards in the public interest" and "there is no determination of guilt with respect to any offence provision"[346]. Similarly, a decision to cancel a broadcasting licence for breach of licence conditions is a harsh consequence but it can be made as an administrative decision to protect the public interest even if the conduct might separately be found to be an offence[347].
The extent of the harshness of the consequence imposed by a law can assist in drawing a line between (i) consequences that sanction proscribed conduct and are thus for the purposes of punishment, and (ii) consequences that respond to other public interests although they rely upon a person's conduct as a factum. The harsher the consequence, the more likely it is that the law will be interpreted as a response to proscribed conduct. Extremely harsh consequences can rarely be justified, and hence are rarely imposed upon people, other than as responses to proscribed conduct. This is the reason that the imposition of the extreme consequence of detention is "likely to permit an inference to be drawn that, for some reason, the legislature wishes to punish the person to be detained"[348].
Nevertheless, there will be some circumstances where a law will not be characterised as punitive despite an extremely harsh consequence such as detention. As I explained in Minister for Home Affairs v Benbrika[349], a person with an extreme mental or physical illness might be detained by the State in a psychiatric institution or in a quarantine facility. That detention is solely for the public purpose of protection of the person and the public. It is "purely protective"[350]. It is not for the purpose, in whole or in part, of sanctioning proscribed conduct. Indeed, a person detained might not have engaged in any proscribed conduct.
By contrast, detention is plainly punitive when it is imposed as part of a sentence for an offence for purposes which include sanctioning an offender's conduct and preventing and deterring further offending. If that punishment is then continued, thus exceeding what the offender individually deserves for their conduct, it does not cease to be punitive. Indeed, it becomes more punitive. An example is a detention order made prior to the commencement of a person's sentence of imprisonment for an offence, ordering that on the expiration of the term of imprisonment the person be detained indefinitely at the Governor's pleasure for the protection of society[351]. The same is true of orders for continuing detention made at the end of a person's sentence: it is a category error to assume that because those orders have a preventive or protective purpose they do not also serve, at least in part, the purpose of being a sanction for proscribed conduct[352].

Ultimately, I consider that s 36B has a punitive character with a purpose to sanction particular conduct. It is not a law which could be described as having the sole purpose of being "political" or "purely protective". This conclusion is dictated by four reasons.
First, the extreme consequences imposed by s 36B provide significant support for the conclusion that a purpose of the law is to sanction particular conduct. I do not accept the surprising submission of the defendants that the harshness of stripping a person of citizenship under s 36B might be better compared with the temporary disqualification of a person from managing corporations[353] than with detention. The stripping of a person's citizenship, with the usual consequence of deportation or banishment, is in a wholly different league from the temporary disqualification of a person from managing corporations. It involves "the total destruction of the individual's status in organized society"[354]. It has been described as "a fate universally decried by civilized people"[355] and as a form of civil death[356]. Judge Augustus Hand thought it to be "a dreadful punishment, abandoned by the common consent of all civilized peoples"[357].
It must be accepted, however, that even the extreme consequence of stripping a person of their citizenship, with associated deportation or exile, does not necessarily dictate the conclusion that a law is punitive. In Ex parte Walsh and Johnson; In re Yates[358], Isaacs J recognised that the power of deportation might be enacted as "a punishment for crime", in which case it would necessarily be a power to be exercised by the judiciary. But his Honour acknowledged that the power of deportation might alternatively be enacted "as a political precaution ... and possibly on considerations not susceptible of definite proof but demanding prevention or otherwise dependent on national policy". A power of that latter "political" kind was upheld in Falzon v Minister for Immigration and Border Protection[359], in which this Court upheld the validity of the power of the Minister to cancel a person's visa as a step in removing the person from Australia, by reference to "a primary and characteristic factum" of previous criminal offending. The cancellation of the visa was not a sanction for the proscribed criminal offending. Rather, the criminal offending was merely a factum that demonstrated a failure to comply with express or implied conditions for remaining in Australia.
Secondly, the character of a law can be informed by its historical antecedents[360]. Although denationalisation laws commencing with the Naturalization Act 1870[361] recognised denationalisation for non‑punitive purposes, those purposes were generally based upon consent. The long history of non-consensual citizenship stripping or banishment is one strongly associated with punishment. In Roman law, death and exile were capital punishments, with the consequence of exile being "interdiction from fire and water" - that is, deprivation of warmth and food - in the community in which the person had lived[362]. Exile was used as punishment in England, following the example of Rome, as well as in ancient Babylon and Greece[363]. It became most prominent in England with a 1597 statute that provided for various persons classed as criminals to be punished by being "banyshed out of this Realme and all other the Domynions thereof"[364]. Sir Edward Coke's report of Doctor Hussey's Case[365] described banishment as "so great a punishment" and equated it with perpetual imprisonment. The punishment of banishment was reaffirmed by Parliament "at frequent intervals" until 1864[366]. By the end of the 18th century, Hawkins had written of Parliament's prerogative to impose this extraordinary punishment, saying that "no power on earth, except the authority of parliament, can send a subject of England, not even a criminal, out of the land against [their] will"[367].
Thirdly, the punitive character of s 36B is also supported by the statement in s 36A of the purpose of Subdiv C of Div 3 of Pt 2 of the Australian Citizenship Act. That statement of purpose includes the recognition by the Parliament that the common bond of Australian citizenship may be severed by citizens "through certain conduct incompatible with the shared values of the Australian community". The focus upon the breach of norms of conduct shared in the community is an indication, at a lower level of generality, of a purpose of sanctioning that conduct. In particular, the statement of purpose encompasses s 36D, which permits the Minister to determine in writing that a person ceases to be an Australian citizen upon various conditions including the person being convicted of a particularly serious offence. As the defendants conceded, s 36B, like s 36D, has a purpose of deterrence of a particular category of extreme, reprehensible conduct.
Fourthly, the punitive nature of the law is supported by the Minister being the person who, having decided that the conduct was extreme and reprehensible, is also the person who exercises a discretion to determine whether Australian citizenship should cease[368].
Section 36B is invalid as a law that purports to confer exclusively judicial power upon the Executive.

The plaintiff challenges the validity of s 36B of the 2007 Citizenship Act. His principal ground of attack is that s 36B is not authorised by any head of power under s 51 of the Constitution, and, in particular, is not supported by the "naturalization and aliens" head of power in s 51(xix). The defendants accepted that the only head of power that could support the validity of s 36B is s 51(xix).
If it be correct to state that the antonym of a citizen for the purposes of the 2007 Citizenship Act is an alien of this country, then the plaintiff was not an alien within the meaning of s 51(xix) of the Constitution when the Minister exercised the power conferred by s 36B(1) of the 2007 Citizenship Act[370]. That is because he was a citizen. If it be more accurate to state that the essence of alienage is allegiance, not to Australia, but to another sovereign power[371], then, based on the plaintiff's explanation for being in the Syrian Arab Republic ("Syria"), he was also no alien immediately before the Minister exercised the power under s 36B(1). That is because, as McHugh J observed in Singh v The Commonwealth, a person's allegiance to Australia (or the Crown in right of Australia) arises if the person is born in this country[372]. That observation requires qualification in the case of a person born in Australia to parents who are visiting this country on a temporary basis[373]. In Singh, the plaintiff had been born in Australia but was the daughter of Indian citizens who arrived in Australia on "Business (Short Stay) visas"[374]; thus, her parents were only residing temporarily in this country. Given those facts, the plurality concluded that the plaintiff, an Indian citizen by descent, was an alien because of her allegiance to a foreign power attributed to her by the law of India[375]. Here, the plaintiff's parents were not residing in Australia temporarily.
Contrary to the plaintiff's submissions, the issue for determination in this amended special case is not whether s 51(xix) of the Constitution authorises the Federal Parliament to pass a law that banishes a natural‑born citizen. No such law may be found in the 2007 Citizenship Act. Rather, the consequences of possible deportation arise by reason of s 198(2) of the Migration Act 1958 (Cth), which obliges an officer to remove an unlawful non-citizen "as soon as reasonably practicable" from Australia. As the plurality observe[376], and I accept, the practical combined effect of s 36B and the Migration Act is exclusion from this country. Even then, however, once removed the unlawful non‑citizen may be eligible to re‑enter Australia upon the grant of an applicable visa[377]. In the case of the plaintiff, no issue of deportation arises. That is because he has remained abroad since 2013. Whether a grant of a protection visa in the plaintiff's case would be an "unlikely event"[378], to use the language of Kiefel CJ, Keane and Gleeson JJ, remains unknown. Certainly, if one were to accept his version of what had happened to him, he may very well be eligible for the grant of a protection visa. It follows that the issue to be determined is not whether the Federal Parliament may banish a citizen, but rather whether it may validly pass a law that cancels the citizenship of a natural‑born Australian, the concept of citizenship being "entirely statutory" in nature[379]. The authority to do so turns upon the extent to which s 51(xix) authorises Parliament to pass laws concerning the denationalisation or denaturalisation of its citizens.
Originally, and subject to certain exceptions[380], at common law the "stern rule" was that a natural-born subject could not divest herself or himself of her or his allegiance to the Crown[381]. Allegiance was considered to be indelible[382]. As Blackstone wrote[383]:

The foregoing demonstrates that around the time of Federation, both the United Kingdom and the United States recognised various forms of lawful expatriation and denationalisation. In the case of the Naturalization Act 1870, denationalisation took place where, in defined circumstances, a person acted inconsistently with her or his status as a British subject, by, for example, making a declaration of alienage or being naturalised in a foreign state[394]. In the case of the Expatriation Act of 1907, citizenship was forfeited when a person acted inconsistently with being a citizen of the United States, by, for example, taking an oath of allegiance to a foreign state[395]. In neither jurisdiction was it necessary for the person to assent to the loss of nationality. This history supports the proposition that denationalisation may occur when a person acts inconsistently with membership of a body politic by changing her or his allegiance, whether intentionally or not, to a foreign country. The founding fathers were no doubt aware of these developments in the law[396].
Reflecting this history, the Naturalization Act 1903 (Cth) contained provisions that "deemed" a woman to be a British subject who, "not being a British subject", married a British subject[397] and "deemed" an infant "not being a natural-born British subject" to be a British subject in defined circumstances[398]. It also contained a provision that conferred on the Governor-General a power to revoke a "certificate of naturalization" obtained by any "untrue statement of fact or intention"[399]. A similar provision was to be found in s 11 of the Naturalization Act 1903-1917 (Cth) and s 12 of the Nationality Act 1920 (Cth). That Act also provided, amongst other things, that a woman, having been a British subject, was "deemed to be an alien" if she married an alien[400] and that a person was "deemed to have ceased to be a British subject" if she or he became naturalised in a foreign state[401]. In the foregoing examples, the assent of the person was not required.
Some early authorities of this Court perhaps betray differing views about membership of the Empire, British subjecthood and race. In Potter v Minahan[402], Minahan had been born in Victoria of mixed Anglo-Chinese parentage. He left Australia as a child to live in China for 26 years. He then returned to Australia. Each of Griffith CJ, Barton and O'Connor JJ decided that Minahan was not an immigrant for the purposes of the Immigration Restriction Acts 1901-1905 (Cth). Isaacs and Higgins JJ dissented. Griffith CJ said[403]:

The foregoing expression of the width of the aliens power does not draw any distinction, for the purposes of prescribing "the conditions on which citizenship may be acquired and lost"[428], between a natural-born citizen and a naturalised citizen. Any such distinction has now been rejected by this Court[429].
Whilst s 51(xix) of the Constitution authorises Parliament to make laws which prescribe "the conditions on which citizenship may be acquired and lost"[430], that power, consistently with the "qualification" described by Gleeson CJ in Singh[431], is not unfettered. Because membership to the Australian body politic is inextricably bound up with the concept of allegiance to this country, the power to denationalise must be limited to laws that recognise and accept a loss of citizenship arising from actions or steps that are indelibly inconsistent with that allegiance and with membership of that community. That conclusion is consistent with how the law of denationalisation had developed in the United Kingdom and the United States by the time of Federation. It explains Isaacs J's observation in Ex parte Walsh that the Federal Parliament had the power to pass a law that eliminated from "communal society" any person, whether born in Australia or not, who was "inimical" to the "existence" of that society[432]. His Honour referred to "plotting with foreign powers against the safety of the country" and even being "suspected of being a spy or a traitor"[433]. No doubt there are many ways a person may act that are enduringly antithetical to allegiance to Australia, or to membership of the "people of the Commonwealth"[434] that comprise this nation.
It follows that the power to pass a law of denationalisation is not to be limited to a declaration of alienage[435]. Nor would the validity of such a law require an actual intention to renounce citizenship. In Perez v Brownell, Frankfurter J made the following observation in support of that proposition in relation to a law that cancelled a person's citizenship upon voting in a foreign political election. His Honour said[436]:

As already concluded, a law that permits the cancellation of citizenship following conduct which is so incompatible with the shared values of the Australian community that it constitutes a severance of the bond between citizens and a repudiation of allegiance is an example of a valid denationalisation law. It is valid because cancellation takes place when there exists conduct which demonstrates an indelible renunciation of membership of this nation. Section 36B of the 2007 Citizenship Act is a law of this kind.
Section 36B operates when three conditions are met. First, the Minister must be satisfied that a person has engaged in certain types of "conduct"[443]. That "conduct" is prescribed in s 36B(5). Secondly, the Minister must be satisfied that "the conduct demonstrates that the person has repudiated their allegiance to Australia"[444]. Thirdly, the Minister must be satisfied that "it would be contrary to the public interest for the person to remain an Australian citizen"[445]. Pursuant to s 36E, in considering the public interest, the Minister "must" have regard to nine matters. These include "the severity of the conduct" in question, "the degree of threat posed by the person" to the community, whether "the person is being or is likely to be prosecuted" for the conduct, and "Australia's international relations"[446].
The validity of this law hinges on the second condition in s 36B(1). Conduct that manifests a repudiation of allegiance to Australia is conduct that is inconsistent with continued citizenship and membership of this nation. The word "repudiated", in its statutory context, refers to a voluntary rejection or renunciation of allegiance[447]. Whether such a rejection or renunciation has taken place does not turn upon the subjective wishes of a person, but upon an objective consideration of the voluntary "conduct" identified in accordance with s 36B(1)(a). That conduct is examined to determine whether it "demonstrates" the presence of a repudiation of allegiance.
A further element of this statutory scheme is that it only applies to individuals who have dual citizenship. Pursuant to s 36B(2), the Minister cannot determine that a person ceases to be a citizen if the Minister is also satisfied that it would result in the person becoming someone who is not a national or citizen of any country. Thus, the power to cancel citizenship cannot be exercised if it would lead to statelessness. Here, the plaintiff is a citizen of the Republic of Turkey.
The "conduct", defined by s 36B(5), refers to behaviour that potentially contradicts allegiance to the bonds that constitute the nation. With the exception of s 36B(5)(j), the "conduct" listed is connected with terrorism or constitutes terrorism. Terrorism is an evil scourge, which in the 21st century has been visited on this country. It is warfare waged unconventionally[448]. Paragraph (a) of s 36B(5) refers to "engaging in international terrorist activities using explosive or lethal devices". Paragraph (b) refers to "engaging in a terrorist act". Paragraph (c) refers to "providing or receiving training connected with preparation for, engagement in, or assistance in a terrorist act". Paragraph (d) refers to "directing the activities of a terrorist organisation". Paragraph (e) refers to "recruiting for a terrorist organisation". Paragraph (f) refers to "financing terrorism". Paragraph (g) refers to "financing a terrorist". Paragraph (h) refers to "engaging in foreign incursions and recruitment" (addressed in greater detail below). Paragraph (i) refers to "fighting for, or being in the service of, a declared terrorist organisation"[449]. Paragraph (j) refers to "serving in the armed forces of a country at war with Australia".
The foregoing activities are also criminal offences for the purposes of the Criminal Code (Cth), although only if the "fault element" for each offence, as prescribed by the Criminal Code, is satisfied. Thus, s 36B(6) provides that the words and expressions used in s 36(5)(a)-(h) have the same meaning as they do in the Criminal Code[450]; however, this does not include the "fault elements" for each offence.
It is easy to accept that participation in these types of terrorist activities could amount to "conduct" that is necessarily inconsistent with allegiance to Australia or to membership of this nation. For example, s 100.1 of the Criminal Code defines the type of action that can constitute a "terrorist act", for the purposes of s 101.1, as engaged by s 36B(5)(b). It includes action that causes serious physical harm or death[451], which is done with the intention of "advancing a political, religious or ideological cause", and with the intention of, amongst other things, "influencing by intimidation" the Australian government or "intimidating the public"[452]. Whether, by reason of s 36B(6), the intentional attributes of the definition of a "terrorist act" are included need not, for the moment, be resolved. A law that facilitates the cancellation of a person's citizenship for engaging in "terrorist acts", when that person's conduct demonstrates repudiation of allegiance to Australia, and when it is also in the public interest for that person not to remain a citizen, is authorised by s 51(xix). The same conclusion applies to the other types of conduct identified in s 36B(5)(a)-(i) that are connected to, or which further, terrorism. Terrorism is manifestly antithetical to the fundamental values shared by members of the Australian nation.

On the agreed facts of this amended special case, the Minister was satisfied that the plaintiff had engaged in a "foreign incursion" for the purposes of s 36B(5)(h) of the 2007 Citizenship Act. The Minister was also satisfied that this conduct demonstrated that the plaintiff had "repudiated [his] allegiance to Australia" and that it was "contrary to the public interest for [the plaintiff] to remain an Australian citizen".
Pursuant to s 36B(6), one turns to the Criminal Code to determine what a "foreign incursion" comprises. Pursuant to s 119.2 of the Criminal Code, an Australian citizen commits an offence if she or he enters or remains in an area of a foreign country and that area is "declared" by the Foreign Affairs Minister pursuant to s 119.3. The Foreign Affairs Minister may make that declaration if she or he is satisfied that a "listed terrorist organisation is engaging in a hostile activity in that area"[453]. The term "terrorist organisation" is defined to include "an organisation that is directly or indirectly engaged in, preparing, planning, assisting in or fostering the doing of a terrorist act"[454]. The phrase "engage in a hostile activity" refers to conduct that is engaged in with the intention of achieving objectives such as the overthrow of a government of a foreign country by force or violence, causing serious harm or death, intimidating the public, or unlawfully damaging property belonging to the government of a foreign country[455]. Section 119.2(3) lists a series of permitted or innocent purposes for being in such a "declared" area. These include providing humanitarian aid, performing an official governmental duty, performing an official duty for the United Nations or the Red Cross, making a bona fide visit to a family member, and making a news report.
Section 119.2 was enacted in 2014. The Explanatory Memorandum to the Counter-Terrorism Legislation Amendment (Foreign Fighters) Bill 2014 (Cth) described the purpose of s 119.2 in the following terms[456]:

In 2014, the Foreign Affairs Minister declared al-Raqqa province in Syria to be a "declared" area for the purposes of s 119.3 of the Criminal Code[457]. In a statement of reasons accompanying the declaration, it was observed that Islamic State was "based in the Iraqi provinces of Ninewa and al‑Anbar and the Syrian province of al‑Raqqa"[458]. It was further observed that Islamic State's activities and calls "have attracted thousands of 'foreign fighters', including Australians, who have travelled to Syria to join ISIL and engage in hostile activity"[459].
It was also an agreed fact of this amended special case that the plaintiff, at some point after 16 April 2013, travelled to Syria. It was not an agreed fact that he had entered into, and had remained in, al‑Raqqa province after it became a "declared" area. Indeed, prior to his departure, the plaintiff informed his family that the purpose of his travel was to arrange a marriage, and that he intended to return to Australia. That marriage took place in 2013 in the Governorate of Idlib, Syria. The plaintiff's litigation guardian, his sister, claims that while in Syria (prior to his imprisonment) the plaintiff had wanted to return to Australia but was "stuck" as there was "no way to get out" because of road closures. He was subsequently detained at first by Kurdish militia and then by Syrian authorities. He claims he was tortured. He remains in custody in Syria.
The Minister's determination to cancel the plaintiff's citizenship, pursuant to s 36B(1) of the 2007 Citizenship Act, followed the receipt of a Qualified Security Assessment ("QSA") from the Director-General of Security of the Australian Security Intelligence Organisation ("ASIO"). The QSA advised that ASIO had assessed that the plaintiff had "likely engaged in foreign incursions and recruitment by entering or remaining in al‑Raqqa Province in Syria, a declared area, on or after 5 December 2014" and had "likely travelled to Syria in early-to-mid-2013, and had joined the Islamic State of Iraq and the Levant [('ISIL')]". ASIO indicated that the plaintiff's travel to Syria was facilitated through a Sydney‑based facilitation network developed by convicted terrorist Hamdi Al Qudsi. The plaintiff is seeking review of this QSA in the Administrative Appeals Tribunal[460]. The correctness of the QSA and the lawfulness of the Minister's determination under s 36B(1) are not in issue before this Court. The plaintiff has also made an application for revocation of the Minister's decision to cancel his citizenship[461]. He was also aware that he could seek judicial review of the determination.
The plaintiff contended that s 36B(5)(h) is over-inclusive because it extends to conduct that would include a visit to a "declared" area that was wholly innocent. In particular, he relied upon the absence of any fault element for conduct constituting a foreign incursion. However, that submission overlooks the fact that the existence of "conduct", enlivening s 36B(1), is only the first of three tests in the applicable statutory scheme[462].
The second test requires the Minister to be satisfied that the conduct demonstrates that the person has "repudiated their allegiance to Australia"[463]. As the defendants contended, if a visit were truly innocent it would be most unlikely that the Minister would ever be satisfied that such blameless conduct constituted a rejection of allegiance to this country. This is made clear in the Revised Explanatory Memorandum to the Australian Citizenship Amendment (Citizenship Cessation) Bill 2020 (Cth) ("the Cessation EM"), which states[464]:

The plaintiff advanced a number of additional grounds attacking the validity of s 36B of the 2007 Citizenship Act. The first of these was that the Court should imply from the text of the Constitution either an absolute or qualified prohibition on the removal of a person's status as a member of the "people of the Commonwealth", consistently with the use of that phrase in the Constitution[466]. The essence of the argument was that once it is acknowledged that the Constitution recognised the existence of the people of Australia as a distinct community, it followed that the character of that body of people was unalterable by Parliament. Parliament did not have an unfettered ability to define, for example, who were the "people" from whom senators and members of the House of Representatives were to be directly chosen for the purposes of ss 7 and 24 of the Constitution. Alternatively, it was submitted, it should be implied that any exclusion from membership of the "people of the Commonwealth" should only take place through an exercise of judicial power under Ch III of the Constitution. Neither proposition was directly supported by any authority.
It is well established that implications which limit the legislative powers of the Commonwealth can only be drawn when it is necessary to do so to give effect to the text or structure of the Constitution[467]. Here, the suggested implication is unnecessary and conflicts with the scope of legislative authority conferred by the "naturalization and aliens" head of power in s 51(xix) of the Constitution. That head of power, for the reasons already given, authorises laws that provide for the denationalisation of an Australian citizen where that person has acted in a way, or taken a step or steps, that constitutes a permanent repudiation of her or his allegiance to Australia or of her or his membership of this nation. The existence of this legislative power is a complete answer to the implication sought to be propounded by the plaintiff. The relevance of Ch III to laws authorising the expatriation of Australian citizens is otherwise addressed below.

Conduct of the kind identified in s 36B(5)(h) and which demonstrates a repudiation of allegiance to Australia may well constitute a "rejection of civic responsibility".
The plaintiff put his case that s 36B is not supported by a "substantial reason" in several different ways. For the reasons that follow, what might constitute a valid "substantial reason" need not be articulated. That is because the plaintiff's contentions are, in any event and with respect, misconceived.
The plaintiff first contended that s 36B is over-inclusive in the range of conduct it specifies and thus has no "rational connection" to any of the ends it might pursue. That submission should be rejected for the reasons already given. Secondly, the plaintiff then complained that s 36B is not a proportionate law because it deprives him of his citizenship permanently. He relied upon the decision of this Court in Roach, which decided that serious criminal offending could only ever justify a temporary withdrawal of the right to vote[472]. That submission is misconceived for two reasons. First, as the defendants pointed out, it overlooks s 36H, which provides that a person whose citizenship has been cancelled may apply to have that decision revoked. That provision allows the Minister to, amongst other things, revoke the decision if it be in the public interest to do so[473]. It also overlooks the power conferred on the Minister by s 36J(1) to revoke the cancellation of citizenship on the Minister's "own initiative" if that would be in the public interest. Secondly, because the reach of s 36B is unlikely to include wholly innocent conduct and is instead directed at conduct that would justify a conclusion by the Minister that a person has repudiated her or his allegiance to Australia, permanent cancellation, subject to ss 36H and 36J, is a proportionate response to an enduring renunciation of membership of the Australian community.
Finally, the plaintiff submitted that s 36B is a disproportionate law because of other laws that already exist and that achieve similar ends. For example, the Federal Parliament has passed laws addressing the risks of terror-related activities that provide for the cancellation of passports, for the making of preventative detention orders, and for the making of continuing detention orders and control orders[474]. The existence of these means of protecting the Australian community did not justify, it was said, what the plaintiff described as a "broad executive discretion permanently to extinguish the civic rights of any member of the Australian community, exercisable on the Minister's satisfaction that any of a wide range of 'conduct' has occurred, without assessment of any fault element". That characterisation of s 36B is a misdescription of the law. Once again, it ignores the fact that engaging in prescribed conduct is only one of three preconditions to the operation of s 36B. It also disregards the nature of the species of "conduct" listed in s 36B(5). For the reasons already given, each species of conduct is potentially repugnant to, and to that extent thereby inconsistent with, fundamental values that inhere in the community comprising the "people of the Commonwealth".

Here, for three reasons the power exercised by the Minister in cancelling the plaintiff's citizenship was not judicial power. First, it has never been an essentially judicial function to make orders which denationalise a person. At common law, denationalisation and expatriation were not possible. And whilst common law courts ordered transportation of convicts to British colonies throughout the 18th and 19th centuries, those convicts remained British subjects[490].
As explained above, the Naturalization Act 1870 changed the common law. It provided for a British subject to lose her or his status as a subject in defined circumstances. None of those circumstances involved an exercise of judicial power. Nor did they involve any form of punishment. Rather, they recognised the acquisition of alien status upon, for example, a subject becoming naturalised in a foreign state.
Following Federation, early enactments in Australia provided the executive, not the judiciary, with the power of denationalisation or deportation in defined circumstances. Section 11 of the Naturalization Act 1903-1917 conferred such a power on the Governor-General. Section 8AA of the Immigration Act 1901-1925 conferred a power of deportation on the Minister. Section 12 of the Nationality Act 1920 conferred a power on the Governor‑General[491] to revoke a certificate of naturalisation where this had been obtained, for example, by false representation or fraud, or where the person had shown herself or himself to be disaffected or disloyal to the Crown. Section 21 of the Nationality and Citizenship Act 1948, as enacted, conferred on the Minister a power of denationalisation which was similar to that conferred by s 36B. It empowered the Minister to deprive a registered or naturalised citizen of her or his citizenship where, for example, the Minister was satisfied that: the person had shown herself or himself "by act or speech to be disloyal or disaffected towards" the Crown[492]; the person had, during any war in which Australia had been engaged, "unlawfully traded or communicated with the enemy or been engaged on or associated with any business which was to his knowledge carried on in such a manner as to assist an enemy in that war"[493]; or the person was not, at the date on which she or he was registered or naturalised, "of good character"[494]. The Minister could not make such an order in respect of a person unless the Minister was satisfied that it was "not conducive to the public good that that person should continue to be an Australian citizen"[495].
Contrary to what might otherwise be thought, the 152 years of legal history since 1870 cannot be overlooked or dismissed as merely recent. Nor does it matter that many of the historical provisions were concerned with naturalised rather than natural-born citizens or subjects. As already mentioned, if denationalisation is a power that may validly be exercised in the case of a naturalised Australian by the executive in accordance with a law authorised by s 51(xix), no different outcome is justified in the case of those born in this country. Both are citizens who assume the same quality of allegiance, whether expressly in the case of naturalised citizens, or implicitly in the case of those born in Australia.
Secondly, as already mentioned, the task of the Minister here is not to determine whether the conduct identified in s 36B(5)(a)-(h) constitutes the commission of any crime. The Minister is not determining guilt or innocence. The conduct to be examined excludes in each case the fault element provided for in the Criminal Code. Instead, the Minister is required to undertake a distinctly different task. The Minister must first determine whether "the conduct demonstrates that the person has repudiated their allegiance to Australia". That is not an inquiry mandated by any provision of the Criminal Code and it does not form part of the criteria for conviction for any of the crimes referenced in s 36B(5)-(6). The Minister must also examine, having regard to the factors listed in s 36E, whether it would be "contrary to the public interest for the person to remain an Australian citizen". What is in the public interest is a matter more usually, but not invariably, reserved to the executive branch of government[496]. In that respect, some of the mandatory factors to be considered pursuant to s 36E require the formation of subjective judgments[497] (for example, a person's connection to the other country of which they are a national or citizen (s 36E(2)(g))), and at least one raises directly a matter more naturally reserved to the executive branch of government ("Australia's international relations" (s 36E(2)(h))). Again, consideration of the public interest in the way mandated by s 36E does not form any part of the criteria for conviction of the crimes referenced in s 36B(5)-(6). It is a consideration that is foreign to the Criminal Code.
Thirdly, and in contrast to American decisions such as Trop or Kennedy v Mendoza-Martinez[498], the purpose of s 36B is not to punish. If it had been, then it may not have been a valid law. Rather, s 36B serves a legitimate, non‑punitive purpose[499]. Its object, as a matter of substance[500], is not retribution; rather, it is to recognise a person's repudiation of her or his allegiance to Australia and to prescribe a consequence for this repudiation, namely denationalisation. The Cessation EM clearly states that the "purpose" of Subdiv C of Div 3 of Pt 2 of the 2007 Citizenship Act is set out in s 36A[501]. Section 36A makes no reference, either directly or indirectly, or indeed inferentially, to punishment or retribution. Rather, it declares what Parliament considers to be the essential aspect of citizenship: it is a "common bond" which involves reciprocal rights and obligations. It then declares that a person may, by her or his conduct, act in a manner that is incompatible with the community's "shared values". It then further declares that when a person so acts, that may justify a conclusion that the person has "severed" her or his bond with the Australian community and has repudiated her or his allegiance to this country. Cancellation of that person's citizenship, in the circumstances mandated by Subdiv C, is simply the de jure acknowledgement of something which de facto has already occurred, namely that person's rejection of the Australian body politic.
The foregoing gives full recognition to the words of s 36A and to the contents of the Cessation EM. It does not promote form over substance and practical effect. Rather, it reflects the reality of the statute. It is, with very great respect, wrong to conclude that the concern of s 36B is with "retribution for conduct" which is "reprehensible"[502]. Not only does such a conclusion manifestly clash with the expression of purpose set out in s 36A and in the Cessation EM, it also fails to grapple with an essential aspect of s 36B, namely repudiation of allegiance to Australia. A terrorist who has left Australia and has committed a terrorist act or acts which demonstrate the required repudiation of allegiance is most unlikely to care much for Australian citizenship (save for the possibility that it might be used to further some terrorist cause). For her or him, loss of citizenship is no punishment; it might be no more than an inconvenience or an insult. That is because she or he has already abandoned Australia. In that respect, it should be steadily borne in mind that the legislative scheme comprised by s 36B is in substance targeted at those who fundamentally loathe this country and all that it stands for. Those persons are not victims who require the protection of their former country; rather, they are, in substance and as a matter of practical effect, repudiators of Australia.
I otherwise agree with Kiefel CJ, Keane and Gleeson JJ[503] that, in a given case, a possible consequence of an application of s 36B might be the protection of the Australian people. That might be the case where the citizenship of a "foreign fighter" is cancelled. But again, that protective, non-punitive purpose does not result in a conferral by s 36B of judicial power on the executive[504].
In argument it was said that s 36B operated retrospectively and that this revealed its true retributive purpose. That submission is misconceived. First, cancellation takes place with only prospective effect[505]. Secondly, the "conduct" which triggers its application has been unlawful since (at the latest) 1 December 2014[506]. Thirdly, for the reasons already given, if the plaintiff entered into and remained in a "declared" area, his conduct might well have shown a repudiation of the Australian community. For the reasons given by Frankfurter J in Perez, which I prefer, it is of no moment whether the plaintiff subjectively knew at that time that his repudiation of the body politic would lead to the cancellation of his citizenship.
Finally, in support of the conclusion that the power of denationalisation conferred by s 36B does not involve the exercise by the executive of judicial power, Subdiv C expressly preserves the responsibility of the courts to ensure that the power is exercised lawfully. A "note" which appears under s 36B(1) expressly refers to a person's ability to seek review of a determination to cancel citizenship in the High Court under s 75 of the Constitution or in the Federal Court under s 39B of the Judiciary Act 1903 (Cth). The same note appears under s 36H(4) in relation to a decision to refuse an application to revoke a determination made under s 36B(1). In "proceedings under section 75 of the Constitution, or under [the 2007 Citizenship Act] or another Commonwealth Act", a determination made under s 36B(1) is taken to be revoked if a "court finds that the person did not engage in the conduct to which the determination relates" or the court finds that the person "was not a national or citizen of a country other than Australia"[507]. These provisions permit the issues of "conduct" and "dual citizenship" to be considered by a court on their merits. If a court were to find that the Minister had been mistaken in her or his satisfaction that conduct of the kind identified in s 36B(5) had taken place, or that the person in question was not a dual citizen, that person's citizenship is taken never to have ceased[508].
The foregoing finds some support in at least one early decision of this Court. In Ex parte Walsh, Isaacs J referred to a man who was thought "by the whole of the rest of Australia" to be of "so great a danger ... that nothing short of expulsion ... would be an adequate protection to the community"[509]. Isaacs J observed that Parliament could validly pass a law for that person's deportation, and that the exercise of such a power was a matter reserved to the executive branch of government, unless the deportation took place as punishment for a crime. His Honour said[510]:

Alexander v Minister for Home Affairs

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