Plaintiff M68/2015 v Minister for Immigration and Border Protection

The plaintiff, an unauthorised maritime arrival, challenged the lawfulness of the Commonwealth's conduct in securing, funding, and participating in their detention at a regional processing centre on Nauru. The dispute concerned the executive and legislative authority of the Commonwealth to engage in such activities, particularly in light of arrangements entered into with Nauru. The case was heard as a special case stated for the opinion of the Full Court of the High Court of Australia.

The central legal issues before the Court were whether the plaintiff had standing to challenge the Commonwealth's past conduct, and whether that conduct, including the signing of a Memorandum of Understanding with Nauru and giving effect to regional processing arrangements, was authorised by section 61 of the Constitution or by section 198AHA of the *Migration Act 1958* (Cth). The Court was also asked to consider the validity of section 198AHA of the *Migration Act* itself, and whether it was a law with respect to aliens. Further questions related to the lawfulness of the plaintiff's detention under Nauruan law and the potential for future conduct to be authorised.

The High Court determined that the plaintiff did have standing to challenge the Commonwealth's past conduct. It held that the conduct of the Commonwealth in signing the Memorandum of Understanding with Nauru was authorised by section 61 of the Constitution. However, the Court found that section 198AHA of the *Migration Act*, which was relied upon to authorise the Commonwealth's actions in giving effect to the regional processing arrangement, was invalid as it was not supported by any head of Commonwealth legislative power. Consequently, the Court concluded that the Commonwealth's past conduct in securing, funding, and participating in the plaintiff's detention was not authorised by a valid law of the Commonwealth.

The Court answered the stated questions accordingly, finding that the plaintiff had standing and that the conduct was authorised by section 61 of the Constitution but not by section 198AHA of the *Migration Act*, which was held to be invalid. The question of what relief, if any, should be granted to the plaintiff was remitted to a single judge of the Federal Court. The High Court ordered that the defendants pay the costs of the special case and the proceedings generally.