Applicable principles
10 The most pertinent authority on the contentions advanced by the appellants remains the reasons for judgment of Crennan and Bell JJ in Minister for Immigration and Citizenship v SZMDS [2010] HCA 16; 240 CLR 611, especially at [121]-[131]. Their Honours were, with Heydon J, in the majority on the appeal. At [130]-[131] their Honours said:
In the context of the Tribunal's decision here, "illogicality" or "irrationality" sufficient to give rise to jurisdictional error must mean the decision to which the Tribunal came, in relation to the state of satisfaction required under s 65, is one at which no rational or logical decision maker could arrive on the same evidence. In other words, accepting, for the sake of argument, that an allegation of illogicality or irrationality provides some distinct basis for seeking judicial review of a decision as to a jurisdictional fact, it is nevertheless an allegation of the same order as a complaint that a decision is "clearly unjust" or "arbitrary" or "capricious" or "unreasonable" in the sense that the state of satisfaction mandated by the statute imports a requirement that the opinion as to the state of satisfaction must be one that could be formed by a reasonable person. The same applies in the case of an opinion that a mandated state of satisfaction has not been reached. Not every lapse in logic will give rise to jurisdictional error. A court should be slow, although not unwilling, to interfere in an appropriate case.
What was involved here was an issue of jurisdictional fact upon which different minds might reach different conclusions. The complaint of illogicality or irrationality was said to lie in the process of reasoning. But, the test for illogicality or irrationality must be to ask whether logical or rational or reasonable minds might adopt different reasoning or might differ in any decision or finding to be made on evidence upon which the decision is based. If probative evidence can give rise to different processes of reasoning and if logical or rational or reasonable minds might differ in respect of the conclusions to be drawn from that evidence, a decision cannot be said by a reviewing court to be illogical or irrational or unreasonable, simply because one conclusion has been preferred to another possible conclusion.
11 It is also worth noting, in the context of this appeal, what was said by Heydon J at [78] and [86]:
The issue was one on which minds might differ. The Federal Court evidently operated on one assumption or conclusion about that issue. The Tribunal operated on another. The difference was one of degree, impression and empirical judgment. It did not stem from an error in logic by the Tribunal member. The difference could not be said to reveal an absence of any basis whatsoever for her conclusion.
…
The difference between the Federal Court and the Tribunal may be put thus. The Federal Court thought that the first respondent's explanation for not seeking asylum in the United Kingdom was "perfectly plausible". There are pejorative meanings of the word "plausible", but they are not the meanings which the Federal Court was conveying. The Federal Court was saying that the explanation was "capable of being believed" or "apparently believable". The Tribunal, however, did not believe it. Something can be capable of being believed without actually being believed. For the Tribunal member to withhold belief from something which is "perfectly plausible" but which she did not find to have been satisfactorily explained and which she found not to be probable is not illogical.
12 The Minister referred to the decision of CQG15 v Minister for Immigration and Border Protection [2016] FCAFC 146; 253 FCR 496, where the Full Court (at [60]) endorsed the observations of Wigney J in Minister for Immigration and Border Protection v SZUXN [2016] FCA 516. In particular, and properly, the Minister accepted what was said by Wigney J at [54]:
… The judgment of Crennan and Bell JJ in SZMDS reveals that jurisdictional error may be able to be established on the basis of illogical reasoning or illogical or irrational findings "on the way" to the final conclusion (see 648 [132]): see also SZRKT at 137-138 [151]-[153]; SZWCO v Minister for Immigration and Border Protection [2016] FCA 51 at [61]-[62].
13 The Minister submitted, and I agree, that each of the five matters identified on behalf of the appellants in the amended notice of appeal is a finding "along the way" to the Tribunal's ultimate conclusion that it was not satisfied that Australia had protection obligations to the appellants, under either the Refugees Convention (Convention Relating to the Status of Refugees, done at Geneva on 28 July 1951 as amended by the Protocol Relating to the Status of Refugees, done at New York on 31 January 1967), or on the basis of Australia's complementary protection obligations under the CAT (Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, opened for signature 10 December 1984, 1465 UNTS 85 (entered into force 26 June 1987)) and the ICCPR (International Covenant on Civil and Political Rights, opened for signature 16 December 1996, 999 UNTS 171 (entered into force 23 March 1976)).
14 More recently, in considering these kinds of arguments, especially in relation to credibility findings, in Republic of Nauru v WET040 [No 2] [2018] HCA 60; 362 ALR 235 the High Court identified the following kinds of benchmarks:
(a) whether a conclusion of "implausibility" was a "bare assertion" (at [33]);
(b) whether factual considerations identified by a decision-maker as reasons to reject a narrative or an account were nothing more than speculation or conjecture (at [29]);
(c) whether an inference drawn by a decision-maker was a "rational inference" (at [28]); and
(d) whether a conclusion was "unsupported by basic inconsistencies" (at [31]).
15 In Minister for Immigration and Border Protection v Stretton [2016] FCAFC 11; 237 FCR 1 at [57], Griffiths J also observed that the concept of proportionality may have a role to play in irrationality or legal unreasonableness. His Honour said, by reference to the plurality's judgment in Minister for Immigration and Citizenship v Li [2013] HCA 18; 249 CLR 332:
The concept of "unreasonableness" can accommodate individual heads of judicial review, including a "proportionality analysis by reference to the scope of the power" (at [73]). Thus, although the argument was not presented in this way in Li itself, the plurality stated that, if the Migration Review Tribunal gave "excessive weight" to the question whether the visa applicant had had an opportunity to present her case, "an obviously disproportionate response is one path by which a conclusion of unreasonableness may be reached (at [74]). It may be interpolated at this point that, in the recent decision in McCloy v New South Wales [2015] HCA 34 at [3], French CJ, Kiefel, Bell and Keane JJ described the term "proportionality" in Australian law as describing a class of criteria:
…to determine whether legislative or administrative acts are within the constitutional or legislative grant of power under which they purport to be done.
(Emphasis added.)
This may indicate that the concept of proportionality is an aspect of judicial review of administrative action.
(Original emphasis.)
16 One of the issues not yet well-developed in current Australian administrative law is how the concept of legal unreasonableness operates when the attack is not on an exercise of power. In Minister for Immigration and Border Protection v SZVFW [2018] HCA 30; 357 ALR 408 at [53], Gageler J said:
Whatever room might remain for argument about the most appropriate expression of the standard of legal reasonableness, however, the nature of legal unreasonableness should be taken to be settled by the explanation of it in Quin. The requirement that a statutory power be exercised within the bounds of reasonableness is an implied condition of the statutory conferral of the power. The implication arises through operation of a common law presumption of statutory interpretation that a statutory power is conferred on condition that the power can be exercised only within those bounds. The presumption prevails to condition the exercise of the power on the repository complying with the standard of legal reasonableness absent statutory indication that the repository must meet some higher standard (an example of which is where the repository is restricted to exercising the power only on reasonable grounds) or will sufficiently comply with the statute by meeting some lower standard (an example of which is where the statute requires no more than that the repository exercise the power in good faith and for a purpose permitted by the statute). Where the presumption prevails so as to condition the exercise of the power on the repository complying with the standard of legal reasonableness, a decision made or action taken in purported exercise of a statutory power in breach of the standard of legal reasonableness is a decision or action which lies beyond the scope of the authority conferred by the power.
(Footnotes omitted.)
17 This description of the operation of legal unreasonableness, with which I respectfully agree, focuses on an exercise of statutory power. Thus, the concept sits comfortably with the circumstances in Li and in Minister for Immigration and Border Protection v Singh [2014] FCAFC 1; 231 FCR 437, both of which concerned the statutory power of a Tribunal to adjourn a review from time to time. So too, the concept sits comfortably with an "outcome-focussed" analysis of an exercise of power such as the decision to cancel a visa: see Stretton at [21]-[22] (Allsop CJ), [62] (Griffiths J) and [92] (Wigney J).
18 So far as I am aware, at least at the level of the High Court or the Full Court of this Court, since Li the concept of legal unreasonableness has not been applied to individual aspects of the fact-finding of a decision-maker or a Tribunal in the way it is put in this appeal. Counsel for the Minister agreed this was the case. Of course, insofar as the two principal judgments in SZMDS refer to legal unreasonableness as well as irrationality or illogicality, it might be said to have occurred in that context, but since that judgment, the two kinds of jurisdictional error appear to have gone their separate ways somewhat. In this appeal, counsel for the Minister accepted there did not appear to be any decisions invoking legal unreasonableness in this kind of context, and referred to what was said by two members of the Full Court in Gupta v Minister for Immigration and Border Protection [2017] FCAFC 172; 255 FCR 486 at [36].
19 That being the state of the law as far as I can ascertain it, I have focussed more on the irrationality arguments, which sit comfortably within existing authorities.