Did AAT have power to determine legality of Minister’s decision?

Summary of relevant events:

1. The Respondent entered Australia by boat without a visa.
2. "He was taken to what was then thought to be a “proclaimed port” (as defined in the Migration Act 1958 (Cth)) in the Territory of Ashmore and Cartier Islands".
3. For several years, the Respondent’s case was dealt with on the assumption he was an "unauthorised maritime arrival" (UMA), as defined in the Migration Act. However, that assumption was incorrect, as the Full Court of the Federal Court (FCAFC) held on 6 August 2018 in DBB16 that the Minister had no power to appoint the Western Lagoon at Ashmore Reef as a "proclaimed port" for the purposes of s 5(5), and that a 2002 declaration to that effect was invalid. As a result, the Respondent was never a UMA.
4. On 14 October 2014, the Minister purported to grant the Respondent:
   1. a Temporary Safe Haven visa (hereafter the "temporary visa") valid for 1 week
   2. a bridging visa valid for 12 months
5. On 1 December 2015, on the incorrect assumption that the Respondent was a UMA, "the Minister purported to exercise his power under s 46A(2) of the Migration Act in respect of a group of persons (including [the Respondent]) to determine that the bar in s 46A(1) to the making of a valid application for a visa did not apply to them if they applied for, relevantly, a SHEV". In reality, the bar never applied to the Respondent, as he was never a UMA.
6. On 18 September 2017, the Respondent applied for a Safe Haven Enterprise visa (SHEV).
7. On 18 July 2018, a delegate refused to grant him the SHEV.
8. The Respondent applied to the Tribunal for review of the delegate’s decision under Pt 7 of the Migration Act.
9. The issue before the Tribunal was whether the SHEV application was valid. It would be invalid if the Respondent held the temporary visa. That was because of ss 91J and 91K of the Migration Act, which were to the effect that a person who held a temporary visa could not validly apply for any other visa, including a SHEV. The Respondent held a temporary visa if the grant of such a visa had been valid. As a result, the ultimate question to the Tribunal was whether the grant of the temporary visa was valid. If so, the Applicant would be barred by s 91K from making a valid SHEV application. Otherwise, he would not be barred.
10. The Tribunal found that the grant of the temporary visa had been invalid, with the result that the Respondent did not hold that visa and therefore was not barred by s 91K from validly applying for the SHEV. The Tribunal further found that the Respondent satisfied s 36(2)(a). As a result, it remitted the application for a SHEV to the Minister with a direction that the Respondent satisfied the criterion for the grant of a SHEV in s 36(2)(a).
11. The Minister applied to the Federal Court for judicial review of the Tribunal's decision and the matter was heard by the FCAFC.
12. Before the FCAFC determined the matter, the Minister granted the Applicant a SHEV.

Some of the questions to the FCAFC were as follows:

Question 1: Can it be said that, despite the late grant by the Minister of a SHEV, the matter did not become moot, as the FCAFC's determination would affect subsequent applications for visas by the Respondent?

Question 2: Was the Minister's assumption that the Respondent was a UMA a legal or a factual error?

Question 3: Did the incorrect belief that the Respondent was subject to the bar under s 46 involve a legal or a factual error?

Question 4: The FCAFC said: "The power in s 195A is conditioned on the Minister thinking that it is in the public interest to grant the visa". Is it an implied condition that the state of mind called for by s 195A, namely that the Minister thinks that it is in the public interest to grant the visa, be formed on the basis of a correct understanding of the law, with the result that a decision under s 195A based on an incorrect understanding of the law might be vitiated with jurisdictional error?

Question 5: Did the Minister’s view that it was in the public interest to grant the Temporary Safe Haven visa proceed on the basis of an incorrect understanding of the law, as the Minister would not have granted the Temporary Safe Haven visa had he not thought that the Respondent was a UMA?

Question 6: Can it be said that, "in truth [the Respondent] was not subject to any bar, and the effect of the decision [to grant him the temporary visa under s 195A] was to [purportedly] subject [him] to a bar when none previously applied to him"?

The FCAFC answered those questions as follows: