French CJ, Gummow, Hayne, Heydon, Crennan, Kiefel, Bell JJ
Administrative law – Procedural fairness - Error of law - Refugees - Migration - Offshore processing - Plaintiffs were "offshore entry persons" under Migration Act 1958 (Cth) ("Migration Act") - Plaintiffs detained under s 189(3) of Migration Act - Each claimed Australia owed him protection obligations under Refugees Convention as amended by Refugees Protocol - Each plaintiff precluded from making valid visa application unless Minister decided in public interest to allow s 46A of Migration Act - Minister had power to grant visa in absence of valid application s 195A of Migration Act - Each plaintiff subject to "Refugee Status Assessment" by departmental officer and subsequent "Independent Merits Review" by independent contractor - Each departmental officer and independent reviewer concluded plaintiff not a person to whom Australia had protection obligations - Powers under ss 46A and 195A "may only be exercised by the Minister personally" - Minister not under duty to consider whether to exercise power under s 46A or s 195A - Whether continuing detention lawful because assessment and review were steps taken under and for purposes of Migration Act - Whether Minister had decided to consider exercising power under s 46A or s 195A of Migration Act in every case where an offshore entry person claimed to be owed protection obligations - Whether those who conducted assessment and review bound to afford procedural fairness to plaintiffs and act according to law - Whether each review procedurally fair and undertaken in accordance with law.
Constitutional law (Cth) – Validity of Commonwealth laws - Section 75(v) of Constitution - Whether s 46A of Migration Act invalid because consideration of exercise of power could not be enforced - Whether Minister's power arbitrary.
High Court – Original jurisdiction - Constitutional writs and orders - Minister not bound to consider exercising powers under s 46A or s 195A of Migration Act - Whether mandamus available - Whether certiorari would have practical utility - Whether declaration would produce foreseeable consequences for the parties.
Words and phrases – "Carltona principle", "excised offshore place", "Independent Merits Review", "offshore entry person", "Pacific Strategy", "Refugee Status Assessment", "unlawful non-citizen".