1. The following uncontentious background facts were set out in Mr Nam's witness statement dated 14 March 2025 and in the Respondent's Statement of Facts, Issues and Contentions dated 10 March 2025:

(a) Mr Nam is 36 years old and holds a private and commercial pilot licence. > > (b) He was first granted an unconditional class 1 Medical Certificate in 2013. > > (c) In November 2020, he was diagnosed with ADHD by Dr David Tofler, a psychiatrist, who provides ongoing treatment. He last flew an aeroplane on 10 December 2020. In April 2021, he was first prescribed methylphenidate at a dose of 10mg, four times a day, to treat his ADHD. > > (d) Mr Nam's Class 1 Medical Certificate expired on 20 June 2018. His Class 2 Medical Certificate was suspended by the Respondent on 4 January 2021 and then cancelled on 4 March 2021, due to his ADHD diagnosis. > > (e) On 11 June 2021, Mr Nam applied for a Class 1 and Class 2 Medical Certificate. > > (f) On 10 August 2022, the Respondent refused to issue a Class 1 and Class 2 Medical Certificate (the Original Decision). The refusal was due to the ADHD diagnosis and the treatment of the condition using methylphenidate hydrochloride. > > (g) On 22 September 2022, the Applicant lodged an application in the Administrative Appeals Tribunal for review of the Original Decision and the matter proceeded to a hearing before the First Tribunal on 11 and 12 September 2023. > > (h) On 2 November 2023, the First Tribunal delivered its decision and ordered that the Original Decision be set aside and remitted the matter to the respondent for reconsideration subject to a direction that 'the applicant does not fail to satisfy the safety relevant condition criterion or the medication criterion by reason of his ADHD, his use of Ritalin or a combination thereof.' > > (i) The references to the safety relevant condition criterion and the medication criterion are references to two of the 39 criteria that must be satisfied to meet the medical standard for each of a Class 1 and a Class 2 Medical Certificate (described below in items 1.1 and 1.3 of Table 67.150 and items 2.1 and 2.3 of Table 67.155 of the Regulations). > > (j) On 23 July 2024, CASA made the Reviewable Decision. > > (k) On 23 July 2024, Mr Nam lodged an application with the Tribunal for review of the Reviewable Decision. > > (l) On 28 February 2025, Mr Nam's dosage was changed to a single daily dose of 40mg of methylphenidate (long-acting formulation).

1. Section 3A of the Civil Aviation Act 1988 (Cth) (the CA Act)[1] provides that its 'main object is to establish a regulatory framework for maintaining, enhancing and promoting the safety of civil aviation, with particular emphasis on preventing aviation accidents and incidents'. Section 9 sets out CASA's functions. Section 9A provides that in exercising its powers and performing its functions, CASA must regard the safety of air navigation as the most important consideration. Section 11 provides that CASA shall perform its functions in a manner consistent with the obligations of Australia under the Chicago Convention and any other agreement between Australia and any other country or countries relating to the safety of air navigation.
2. Part 67 of the Regulations sets out the medical standards for the issue of medical certificates and provides for the issue and administrative control of medical certificates. A person holding a civil aviation licence is required to hold a current medical certificate appropriate to the class of licence. Regulation 61.410 provides that holders of private pilot licences must hold a class 1 or class 2 medical certificate.
3. Pursuant to regulation 67.150, a person who satisfies the criteria in table 67.150 meets medical standard 1:

Abnormalities, disabilities and functional capacity

Has no safety - relevant condition of any of the following kinds that produces any degree of functional incapacity or a risk of incapacitation:

(d) a sequela of an accident or a surgical operation

Is not using any over - the - counter or prescribed medication or drug (including medication or a drug used to treat a disease or medical disorder) that causes the person to experience any side effects likely to affect the person to an extent that is safety - relevant

1. Pursuant to regulation 67.155, a person who satisfies the criteria in table 67.155 meets medical standard 2:

Abnormalities, disabilities and functional capacity

Has no safety - relevant condition of any of the following kinds that produces any degree of functional incapacity or a risk of incapacitation:

(d) a sequela of an accident or a surgical operation

Is not using any over - the - counter or prescribed medication or drug (including medication or a drug used to treat a disease or medical disorder) that causes the person to experience any side effects likely to affect the person to an extent that is safety - relevant

1. Regulation 67.015 gives a meaning to safety-relevant by providing that a medically significant condition is safety-relevant 'if it reduces, or is likely to reduce, the ability of someone who has it to exercise a privilege conferred or to be conferred, or perform a duty imposed or to be imposed, by a licence that he or she holds or has applied for'.
2. A person may apply to CASA pursuant to regulation 67.175 for the issue of a medical certificate. Regulation 67.180 provides for the issue and refusal of medical certificates. It says relevantly:

(1) Subject to ... regulation 11.055, on receiving an application under regulation 67.175, CASA must issue a medical certificate to the applicant if the applicant meets the requirements of subregulation (2).

(i) the applicant meets the relevant medical standard; or

(ii) if the applicant does not meet that medical standard--the extent to which he or she does not meet the standard is not likely to endanger the safety of air navigation; ...

1. Subpart 11.BA of Part 11 of the Regulations contains rules about granting authorisations including regulation 11.055 which relevantly provides that:

(1A) Subject to subregulations (1B) and (1C), if a person has applied for an authorisation in accordance with these Regulations, CASA may grant the authorisation only if:

(a) the person meets the criteria specified in these Regulations for the grant of the authorisation; and

(e) granting the authorisation would not be likely to have an adverse effect on the safety of air navigation.

1. I note that subregulations (1B) and (1C) of regulation 11.055 have no application.
2. Subregulation 11.055(1) provides that this regulation applies despite any other provisions of the Regulations that provides for the grant or issue of an authorisation. This subregulation, together with subregulation 11.055(1A), were inserted in 2011 to recast how an application for an authorisation is to be dealt with.[2]
3. Regulation 11.055 uses the language of an authorisation which is defined in regulation 11.015 as follows:

(iii) the appointment of an authorised person; or

(b) an approval or qualification of a document or thing under these Regulations, other than a material, part, process or appliance to which regulation 21.305A applies; or

(c) a certificate capable of being granted to a person under these Regulations.

Note: For the definition of civil aviation authorisation, see section 3 of the Act.

1. Section 3 of the CA Act defines civil aviation authorisation as:

"civil aviation authorisation" means an authorisation under this Act or the regulations to undertake a particular activity (whether the authorisation is called an AOC, permission, authority, licence, certificate, rating or endorsement or is known by some other name).

1. It follows that an authorisation would include the issuing of a medical certificate under regulation 67.180.

The Interplay between Regulations 11.055 and 67.180

1. Mr Nam submits that in practical terms, for medical issues, there is no real difference between the concept of safety relevance in Part 67 of the Regulations and the safety of air navigation as referred to in regulation 11.055 because both are directed to the safety of air navigation.
2. As a matter of statutory construction, Mr Nam submits that regulation 11.055(1A)(e) is directed towards fitness and propriety as opposed to the immediate (medical) qualifications required for the authorisation. Mr Nam submits that his construction is supported by regulation 11.055(4) which identifies factors that CASA may take into account in making a determination under regulation 11.055(1A)(e). Those factors are:

(a) the applicant's record of compliance with regulatory requirements (in Australia or elsewhere) relating to aviation safety and other transport safety; and

(b) the applicant's demonstrated attitude towards compliance with regulatory requirements (in Australia or elsewhere) relating to aviation safety and other transport safety; and

(c) the applicant's experience (if any) in aviation; and

(d) the applicant's knowledge of the regulatory requirements applicable to civil aviation in Australia; and

(e) the applicant's history, if any, of serious behavioural problems; and

(f) any conviction (other than a spent conviction, within the meaning of Part VIIC of the Crimes Act 1914) of the applicant (in Australia or elsewhere) for a transport safety offence; and

(g) any evidence held by CASA that the applicant has contravened:

(ii) a law of another country relating to aviation safety; or

(iii) another law (of Australia or of another country) relating to transport safety; and

(h) in the case of an authorisation referred to in subregulation 11.040(2), the applicant's financial standing and financial stability; and

(i) any other matter relating to the fitness of the applicant to hold the authorisation.

1. The factors that under regulation 11.055(4) "CASA may take into account" are not exhaustive. In my view, the fact that these non-exhaustive factors relate to the fitness of the Applicant to hold the authorisation does not mean that one should read down the clearly expressed qualification in regulation 11.055(1A)(e) that CASA may grant the authorisation only if it would not be likely to have an adverse effect on the safety of air navigation. Confining the role of regulation 11.055(1A)(e) to a consideration of fitness and propriety would not achieve the object of promoting the safety of civil aviation,[3] and would not be consistent with CASA's duty when exercising its powers and performing its functions to regard the safety of air navigation as the most important consideration.[4]
2. The interpretation contended for by Mr Nam is contrary to the approach of the First Tribunal and it is also contrary to the plain meaning of the words in regulation 11.055(1A)(e) interpreted in the context of regulation 11.055(1A)(a).
3. Regulation 11.055(1A) relevantly provides that:

... if a person has applied for an authorisation in accordance with these Regulations, CASA may grant the authorisation only if:

(a) the person meets the criteria specified in these Regulations for the grant of the authorisation; and

(e) granting the authorisation would not be likely to have an adverse effect on the safety of air navigation.

1. The "criteria specified" referred to in regulation 11.055(1A)(a) would include the criteria for meeting medical standard 1 in regulation 67.150 and medical standard 2 in regulation 67.155. In other words, regulation 11.055(1A)(a) operates in this case to pick up the terms of regulation 67.180. Mr Nam says that it is difficult to envisage a circumstance where the granting of a medical certificate to a person who complies with the medical standard might have an adverse effect on the safety of air navigation,[5] but that is not to the point. Mr Nam's reliance on Anthony Hordern v ACATUA[6] is misconceived because regulation 67.180 is expressly stated to be subject to regulation 11.055. Regulations 11.055(1A)(a) and (e) are cumulative and must both be satisfied in order to exercise the power to issue a medical certificate. The approach mandated by regulation 11.055(1A) is to consider first whether the criteria specified in the Regulations are satisfied pursuant to regulation 11.055(1A)(a) and then (assuming that regulations 11.055(1A)(b), (c) and (d) are satisfied) to consider whether granting the authorisation would not be likely to have an adverse effect on the safety of air navigation pursuant to regulation 11.055(1A)(e). It is this second step that the Tribunal is tasked to do on this application.
2. When CASA (and the Tribunal standing in the shoes of CASA) is deciding whether to grant an authorisation, including a medical certificate under regulation 67.180, the most important consideration remains the safety of air navigation[7] rather than the fact that Mr Nam may satisfy the criteria for a medical certificate. Regulation 11.055(1A) should be interpreted to mean that if there remains a safety issue even after satisfaction of the criteria in Part 67 then a medical certificate should not be issued.
3. The obligation in regulation 67.180 to issue a medical certificate is expressed as being subject to regulation 11.055, which includes subregulation 11.055(1A)(e). In statutory drafting, the term 'subject to' is used to indicate that a provision must be read as conditioned by other statutory provisions or statutes, as specified.[8] Where there is no conflict between statutory provisions, the expression has no operation, but where there is conflict, the expression indicates which provision must prevail: C & J Clark Ltd v Inland Revenue Cmrs.[9] It follows that regulation 11.055 prevails when considering the interplay with regulation 67.180. This is confirmed by regulation 11.055(1) which says that this regulation applies despite any other provision of the Regulations that provides for the grant or issue of an authorisation.
4. The effect of making regulation 67.180 subject to regulation 11.055 is to add a further condition to the obligation of issuing a medical certificate. The relevant parts of the two regulations when read together provide that subject to the granting of the authorisation being likely to have an adverse effect on the safety of air navigation, CASA must issue a medical certificate to the Applicant if the Applicant meets the requirements of subregulation 67.180(2). This means that if there remains a safety issue even after satisfaction of the criteria for a medical certificate in regulation 67.180, then CASA will not issue the medical certificate. The overarching principle to be derived from the Regulations is that CASA must not issue an authorisation if to do so would have an adverse impact on the safety of air navigation. This is entirely consistent with the express objects of the CA Act.

1. The Tribunal is reviewing a decision made by CASA on a remittal. The First Tribunal exercised the power under s 43(1)(c)(ii) of the Administrative Appeals Tribunal Act 1975 (Cth) to set aside the initial CASA decision and to remit the matter for reconsideration in accordance with directions. CASA had been ordered by the First Tribunal to reconsider its earlier decision subject to a direction that:[10]

the applicant does not fail to satisfy the safety relevant condition criterion or the medication criterion by reason of his ADHD, his use of Ritalin or a combination thereof.

1. In exercising its review powers, this Tribunal is subject to the same constraints as CASA and must approach its task as though it were performing the functions of CASA on the remittal.[11] The task of the Tribunal, as set out by the High Court in Frugtniet at [51]:

... is to stand in the shoes of the decision-maker whose decision is under review so as to determine for itself on the material before it the decision which can, and which it considers should, be made in the exercise of the power or powers conferred on the primary decision-maker for the purpose of making the decision under review. The AAT exercises the same power or powers as the primary decision-maker, subject to the same constraints. The primary decision, and the statutory question it answers, marks the boundaries of the AAT's review. The AAT must address the same question the primary decision-maker was required to address ...

1. The High Court in Frugtniet was not considering the power to be exercised when reviewing a remittal decision but the same principles apply, namely that the Tribunal must exercise the same powers, subject to the same constraints, as the original decision-maker, CASA. The directions imposed on CASA by the First Tribunal must be followed by the Tribunal on this review. This Tribunal may not revisit the matters that were determined by the decision of the First Tribunal.[12]
2. The criteria in issue before the First Tribunal were items 2.1 and 2.3 in Table 67.155 of Part 67 in the Regulations, which were described respectively as the safety relevant condition criterion and the medication criterion.
3. The First Tribunal found, at least impliedly, that Mr Nam met the criteria for medical standard 2 under regulation 67.155 (together with medical standard 1 under items 1.1 and 1.3 of regulation 67.150 which are in the same terms). I say 'at least impliedly' because the First Tribunal expressed itself using a double negative, namely that it was not satisfied that the two criteria were not satisfied.[13] The basis for the First Tribunal's findings was that:

(a) Mr Nam's ADHD was not a safety-relevant condition for the purposes of item 2.1 of Table 67.155; and > > (b) Mr Nam's use of Ritalin did not cause him to experience any side effects for the purpose of item 2.3 of Table 67.155.

4. It would not be open to the Respondent to challenge these findings nor the facts that underpinned them. It is my view that the Respondent does not do so for the reasons set out below.
5. I note that the First Tribunal did not directly address the third element of the criteria in item 2.3 that there are side effects likely to affect the person to an extent that is safety-relevant. The First Tribunal did not need to address that element because it was not satisfied that Mr Nam experienced side effects.[14] It follows that the First Tribunal made no relevant findings as to the risk of side effects.
6. Further, the First Tribunal did not hear any submissions nor make any findings in relation to whether the issuing of a medical certificate "would not be likely to have an adverse effect on the safety of air navigation" under regulation 11.055(1A)(e).[15] The First Tribunal said that:[16]

... any concerns as to air safety ... would appear, at least arguably, to be addressed by other CASR provisions not the subject of submission in these proceedings (such as CASR 11.055).

1. The focus of the First Tribunal was on whether Mr Nam's ADHD was a safety relevant condition and whether Mr Nam experienced any requisite side effects from his use of Ritalin. The focus of this Tribunal is to determine the likely effect of issuing a medical certificate to Mr Nam, a person who takes Ritalin to treat his ADHD. If there is likely to be an adverse effect on air safety as a result, then the medical certificate will not be issued.
2. Given that a medical certificate may only be issued if to do so "would not be likely to have an adverse effect on the safety of air navigation",[17] one would have expected that the issue of regulation 11.055 would have been raised in the First Tribunal at the same time as consideration of regulation 67.180 and the criteria in regulations 67.150 and 67.155. The First Tribunal provided no explanation for why there were no submissions in relation to regulation 11.055 but merely noted as follows:[18]

[4] In deciding whether to issue a medical certificate to the applicant, a constraint to which the respondent was subject (and, hence, one to which the Tribunal is subject) is found in CASR 67.180(1). That regulation imposes an obligation to issue medical certificates for which application is made if the applicant meets certain requirements specified in the regulation.

[5] The obligation to issue a medical certificate for which application is made is, however, subject to another provision of CASR. Under that other provision, a medical certificate may only be issued if, amongst other things, issuing the certificate would not be likely to have an adverse effect on the safety of air navigation.

[6] Neither party made any submissions about the applicability or otherwise of this other CASR provision. The focus of the parties' submissions was, instead, on the question of whether the applicant met the relevant requirements of CASR 67.180. Indeed, only one of the requirements was in issue, it being implicitly accepted by the parties that the applicant met the other relevant requirements.

1. The First Tribunal adopted what may be considered as a narrow approach to the meaning of the medication criterion in item 1.3 of regulation 67.150 and item 2.3 of regulation 67.155:[19]

[82] While, as mentioned earlier, it is appropriate to err on the side of caution when construing CASR, the importance attributed to the safety of air navigation in the legislative context does not constitute a licence for decision makers to ignore the plain meaning of the words used in CASR. This is the more so where any concerns as to air safety that might be said to arise as a result of giving effect to the plain meaning of those words would appear, at least arguably, to be addressed by other CASR provisions not the subject of submission in these proceedings (such as CASR 11.055).

[83] Non-satisfaction of the medication criterion requires that a drug be used by the person concerned "...that causes the person to experience any side effects likely to affect the person to an extent that is safety-relevant." The words of the medication criterion make at least two things plain, even when read as a whole. First, the focus is on the person concerned. Second, that person must experience side effects. A person does not experience side effects from use of Ritalin simply because there is a substantial or real risk of a side effect being experienced by a person who uses Ritalin.

[84] Hence, while we accept that there is a risk that side effects will be experienced by those who use Ritalin, that risk does not mean that the applicant ought to be considered to experience side effects.

1. The First Tribunal made it clear that the presence of a risk of a side effect for a person using Ritalin does not satisfy the criterion in item 1.3 of regulation 67.150 and item 2.3 of regulation 67.155. The First Tribunal took comfort that the issue of risk is addressed by regulation 11.055. This approach by the First Tribunal is consistent with the interpretation contended for by the Respondent (with which I agree) that the role of regulation 11.055(1A)(e) is to provide a mechanism that enables CASA to address residual risk associated with the grant of an authorisation, and to only grant authorisations that would not be likely to have an adverse impact on the safety of air navigation. The First Tribunal did not consider this residual risk and remitted consideration of it to CASA. This Tribunal, adopting its powers on review, would be derelict in its duties if it failed to consider this issue raised by regulation 11.055(1A)(e) on its plain meaning.

Would Granting the Authorisation be likely to have an Adverse Effect on the Safety of Air Navigation?

1. I must consider whether, pursuant to regulation 11.055(1A)(e), granting the authorisation to Mr Nam, in the form of a class 2 medical certificate, would not be likely to have an adverse effect on the safety of air navigation. I confirm that in doing so I accept the findings made by the First Tribunal that:

(a) Mr Nam's ADHD was not a safety-relevant condition for the purposes of item 2.1 of Table 67.155; and > > (b) Mr Nam's use of Ritalin did not cause him to experience any side effects for the purpose of item 2.3 of Table 67.155.

2. The use of the term "likely" in regulation 11.055(1A)(e) requires there to be a substantial or real and not remote chance.[20] In Hall and Civil Aviation Safety Authority,[21] Deputy President Handley said at [45]:

... the assessment of what is "likely" cannot be based on statistical likelihood. In this context, it is a matter of weighing up the requirements of air safety with the applicant's interest in the safe exercise of the privileges and performance of the duties associated with holding a private pilot's licence.

1. In Re Mulholland and Civil Aviation Safety Authority[22] at [65] the Tribunal concluded that the applicant would likely endanger the safety of air navigation because he had "a risk of incapacitation which is significantly different to the remainder of the aviator population who do not suffer from ... [a] safety-relevant medical condition."
2. In this case, I must decide whether the granting of the authorisation would, or would not, be likely to have an adverse effect on the safety of air navigation. This requires a consideration of the likely impact on air safety if the medical certificate were issued. It is trite to say that if that impact was nil or negligible or even beneficial then it would not be an adverse effect. In my view, an adverse effect on air safety for the purposes of regulation 11.055(1A)(e) is one which is material and contrary to the interests of air safety[23] or which has a material impact in a negative or undesirable way. What is required is a material deterioration in the safety of air navigation.
3. Dr David Tofler has treated Mr Nam's ADHD since November 2020. Dr Tofler said in his report dated 12 February 2021 that Mr Nam has had a good response to Ritalin up to 40mgs per day without significant side effects. In a report dated 5 October 2021 Dr Tofler noted that Mr Nam's performance has improved significantly since he commenced treatment with Ritalin. He said that there could be no reason for him not to be able to fly as, if anything, the Ritalin has enhanced his overall performance.
4. Dr Robert Bourke, a clinical neuropsychologist, assessed Mr Nam and provided a report dated 13 July 2021. He said that whilst medicated on Ritalin, Mr Nam had entirely normal and extremely high-level cognitive abilities and that there was no reason, from a cognitive perspective, to preclude Mr Nam from holding a medical certificate and piloting an aircraft. He expressed the opinion that while on medication Mr Nam clearly meets the class 1 medical certificate and class 2 medical certificate from a cognitive perspective.
5. Mr Tim Watson-Munro, a consultant psychologist, examined Mr Nam and provided a psychological assessment dated 13 July 2022 that noted there was nothing to suggest that Mr Nam is not fit to fly from the perspective of his mental health and cognitive capacity.
6. Despites the above positive reports about Mr Nam's mental health and cognitive abilities, the witness statement from Dr Hochberg dated 7 March 2025 provides some insight as to how and why there is a residual risk affecting air safety. The CASA approach to air safety is to identify any risks (in this case from the use of stimulant medication and ADHD) and then identify if there are suitable controls to mitigate the risk to an acceptable level.[24] An important task in analysing risk is to determine risk level which requires consideration of the severity of the consequence and the associated likelihood.[25] Dr Hochberg says that a risk that is not quantified cannot be risk evaluated and he gives a relevant example:

[28] ... there are no established aviation performance requirements that can safely predict the outcome in pilots using performance enhancing medication with variable short-term benefit such as Ritalin or methylphenidate. Consequently, the use of such medication by pilots cannot be risk evaluated. The risk cannot be managed ... . That is why (from a public safety perspective) Ritalin or methylphenidate is wholly banned in all major aviation jurisdictions including Australia for use in pilots.

1. Dr Hochberg explained that ADHD is a neurodevelopment disorder, the essential feature of which is a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. Methylphenidate, which is used to treat ADHD, creates a stimulant effect within the central nervous system. Dr Hochberg referred to a review article from the journal, 'Aviation, Space and Environmental Medicine', which noted:[26]

While there is evidence that pharmacotherapy is effective for the behavioural components of ADHD, even with optimal treatment, neurocognitive impairments persist in ADHD patients. Treated patients perform better on neurocognitive screening tests than untreated patients, but remain significantly impaired compared to normal subjects.

ADHD remains a problematic diagnosis in aeromedical certification. The nature of the neuropsychological deficits of the disorder has significant potential ramifications for safe and efficient flying. The pharmaceutical agents used in the treatment of ADHD in themselves carry unwanted effects and are pharmacokinetically unsuitable for use in civilian aviation.

1. Dr Hochberg lists the intended and unintended effects of the use of methylphenidate which include:[28]

(a) it can mask signs of fatigue; > > (b) it is relatively short acting; > > (c) it can be difficult to identify when its effect starts wearing off; > > (d) there is a potential for adverse effects when the drug is wearing off including decreased mood, impaired alertness, impaired decision-making and reaction time, and possible sudden onset of fatigue; > > (e) it can cause euphoria and have a stimulating effect which may increase risk taking behaviour; > > (f) it can negatively impact lateral thinking (although it may promote concentration); > > (g) it is well known to be associated with physiological and psychological dependence; > > (h) it may cause distracting symptoms like headache, palpitations, dizziness, the Samoan tour disturbances, agitation, confusion, dysphoria, apprehension, delirium, or fatigue; > > (i) it has 198 drug interactions along with 14 disease interactions, and 1 food interaction; and > > (j) it carries a risk of adverse cardiovascular side effects.

2. Dr Hochberg concludes that Mr Nam is at risk, by virtue of him suffering from ADHD and also through the use of methylphenidate, of:[29]

(a) experiencing inattention, difficulties with multitasking in aviation along with deficits in working memory, situation awareness, task prioritisation, task accomplishment, and time management; > > (b) engaging in premature and/or ill considered actions; > > (c) experiencing restlessness and excess of movement causing distraction; > > (d) experiencing impulsivity with excessive involvement in speech or activities resulting in errors; > > (e) experiencing emotional dysregulation or effect of comorbid mental health conditions which may have adverse impact on performance; and > > (f) experiencing, as a consequence of methylphenidate, effects which are both intended and unintended, and which could adversely affect his ability to safely exercise the privileges of a pilot licence.

3. Professor Jonathon Arnold is a consultant pharmacologist who provided reports for CASA dated 21 January and 6 March 2025. In his first report, Professor Arnold said that to the best of his knowledge there is no study assessing the effects of flying and high altitudes on the pharmacology of methylphenidate.[30] Nevertheless, he considered that many of the effects of flying at high altitude might influence the pharmacological effects of methylphenidate as has been shown with other drugs.[31] He concluded that methylphenidate use might pose substantial risks to safety of flying an aeroplane because of the following risks:[32]

(a) There is the risk that methylphenidate might not adequately provide the desired improvements in attention, hyperactivity and impulsivity in ADHD patients due to numerous complicating factors that arise from using methylphenidate as a therapeutic. Interindividual variation in genetics may affect treatment response, which makes it hard to predict how well the medication will exert and maintain its desired therapeutic effects. The effects of flying at high altitudes on the pharmacology of methylphenidate could lead to effective under- and over-dosing that could reduce drug efficacy and increase side-effects. > > (b) Methylphenidate may enhance attention, decision-making, memory and psychomotor performance under the influence of the drug, but in periods where the individual is in the excretion phase there can be withdrawal that leads to the opposite effects: inattention, impaired decision-making, memory deficits and decrements in psychomotor performance. > > (c) There exists a risk of drug dependence and misuse of methylphenidate, which could lead to binge-crash cycles and psychological, social, vocational and recreational issues for the user. > > (d) Methylphenidate has side-effects that have safety implications, for example, headache, increased blood pressure and heart rate that could increase risk of heart attack, dizziness, and psychosis.

4. In his second report, Professor Arnold clarified that there is no specific research assessing the effects of high altitude on how methylphenidate works,[33] but there is some suggestive evidence that high altitude alters dopamine and noradrenaline neurotransmitter systems which could influence the actions of methylphenidate.[34] He said that it is not known whether exposure to high altitudes specifically influences the metabolism of methylphenidate, but there is evidence that high altitudes can affect the metabolism of other drugs which he found concerning and may be relevant to methylphenidate metabolism.
5. Dr Hochberg and Professor Arnold were cross examined at the hearing but there was no real challenge to the above opinions expressed by them. They both referred to the lack of studies assessing the effects of flying whilst using methylphenidate and how, as a result, the risk of flying on methylphenidate cannot be evaluated or managed. In my view, it would be reckless to allow a person on medication for ADHD to fly when the learnings are not sufficiently developed so as to know what effect that medication will have. Despite the lack of relevant studies, both experts expressed concerns as to safety because of their understanding of ADHD and its treatment with methylphenidate. The literature supporting their understanding provides that neurocognitive impairments persist in medicated ADHD patients and that it is the treatment in itself which carries unwanted effects and is unsuitable for use in civilian aviation.
6. Both Dr Hochberg and Professor Arnold maintained their opinion about residual risk even assuming that Mr Nam was now on the slow-release medication.
7. Mr Nam has not flown since he commenced his treatment of methylphenidate in April 2021. It is therefore unknown due to a lack of evidence how the methylphenidate will impact his flying. The fact that he has not experienced any side effects (as found by the First Tribunal and consistent with the opinions expressed by Dr Tofler, Dr Bourke and Mr Watson-Munro) does not mean that, if he were to fly, he would not experience the effects from methylphenidate that pose a risk to air safety as listed by Dr Hochberg and Professor Arnold. Dr Atherton, a psychiatrist with significant experience with pilots and aviation, confirmed in his oral evidence and in his report dated 3 May 2023 the risks associated with flying on methylphenidate and said that the risks cannot be eliminated even if there are no side effects for a while. I consider that the potential for those effects to re-emerge cannot be excluded, and this uncertainty alone has an adverse effect on the safety of air navigation.
8. In my view, the expert evidence from CASA's medical experts supports a finding that issuing the medical certificate and allowing Mr Nam to fly would be likely to have an adverse effect on the safety of air navigation. The evidence as to high cognitive ability and good mental health whilst on Ritalin does not diminish the cogency of the evidence of risk expressed by Dr Hochberg and Professor Arnold and supported by Dr Atherton.
9. Further, issuing a medical certificate to Mr Nam in circumstances where he has been diagnosed as having ADHD and is currently being prescribed methylphenidate, would be contrary to the approach taken by respected flying authorities internationally. Mr Nam's psychiatrist, Dr Tofler, acknowledged in his report dated 22 October 2021 that methylphenidate is a disqualifying medication in Australia, USA, UK and Israel.[35] The approach of overseas flying authorities is relevant because it provides evidence of the risks associated with flying on methylphenidate and because CASA is required to perform its functions in a manner consistent with the obligations of Australia under the Chicago Convention and any other agreement between Australia and any other country or countries relating to the safety of air navigation.

1. In conclusion, I consider that issuing a class 2 medical certificate to Mr Nam would be likely to have an adverse effect on the safety of air navigation because of the risks identified by the CASA medical experts including that effects of flying whilst on methylphenidate have not been properly identified and quantified. It follows that regulation 11.055(1A) is not satisfied and the authorisation sought by Mr Nam should not be granted. The correct or preferable decision is to affirm the decision under review.

I certify that the preceding 58 (fifty-eight) paragraphs are a true copy of the reasons for the decision herein of Deputy President P Britten-Jones.

...................[sgd].....................................................

[1] Civil Aviation Act 1988 (Cth) ('CA Act').

[2] Explanatory Statement, Civil Aviation and Civil Aviation Safety Amendment Regulations 2011 (No. 2) at item 28.

[5] Applicant's Supplementary Contentions dated 1 April 2025 at [13].

[6] [1932] HCA 9; (1932) 47 CLR 1.

[8] Encyclopaedic Australian Legal Dictionary, LexisNexis Australia.

[9] [1973] 1 WLR 905; [1973] 2 All ER 513.

[10] Nam and Civil Aviation Safety Authority [2023] AATA 3574 ('Nam').

[11] See Frugtniet v Australian Securities and Investments Commission [2019] HCA 16 ('Frugtniet').

[12] Re Patricia Marcella Devine and Commonwealth of Australia [1982] AATA 285; (1982) 5 ALN No 22.

[17] Civil Aviation Safety Regulations 1998 (Cth) 11.055(1A)(e).

[20] Re Window and Civil Aviation Safety Authority [1999] AATA 525; (1999) 56 ALD 316.

[21] [2004] AATA 21.

[22] [2007] AATA 1952.

[23] The definition of adverse in the Macquarie online dictionary includes opposing one's interests. See Macquarie Dictionary (online at 20 May 2025) 'adverse' (def 1).

[24] Witness Statement of Dr Anthony Hochberg dated 7 March 2025 at 10 [19].

[26] David J Fitzgerald et al, 'Aeromedical decision making in attention-deficit/hyperactivity disorder' (2011) 82(5)

Aviation Space Environmental Medicine 550, 551-2.

[28] Witness Statement of Dr Anthony Hochberg dated 7 March 2025, 24 [72].

[30] Report of Professor Jonathon Arnold dated 21 January 2025, 3.

[33] Supplementary Report of Professor Jonathon Arnold dated 6 March 2025, 1.