French CJ, Kiefel, Bell, Gageler, Keane, Nettle, Gordon JJ
Migration – Regional processing – Where plaintiff was "unauthorised maritime arrival" upon entry into Australian migration zone – Where plaintiff was removed to regional processing centre on Nauru pursuant to s 198AD of Migration Act 1958 (Cth) – Where Commonwealth entered into arrangement in relation to regional processing functions – Whether plaintiff was detained by Commonwealth at Nauru Regional Processing Centre – Whether principles in Chu Kheng Lim v Minister for Immigration, Local Government and Ethnic Affairs (1992) 176 CLR 1 apply.
Constitutional law (Cth) – Executive power of Commonwealth – Whether conduct of Commonwealth authorised by s 61 of Constitution – Whether conduct of Commonwealth authorised by s 198AHA of Migration Act.
Constitutional law (Cth) – Legislative power of Commonwealth – Whether s 198AHA of Migration Act is a law with respect to aliens – Whether s 198AHA of Migration Act is a valid law of Commonwealth.
Procedure – Standing – Whether plaintiff has standing to challenge lawfulness of conduct of Commonwealth with respect to plaintiff's past detention.
Private international law – Act of State doctrine – Where plaintiff's detention imposed by laws of Nauru – Whether Australian court should pronounce on constitutional validity of legislation of another country.
Words and phrases – "aliens power", "constraints upon the plaintiff's liberty", "control", "detention", "effective control", "memorandum of understanding", "non-statutory executive power", "regional processing country", "regional processing functions".
Constitution – ss 51(xix), 61.
Migration Act 1958 (Cth) – ss 198AB, 198AD, 198AHA