Hamdi v. Rumsfeld

Majority reasoning

The plurality reasoned that Congress's Authorization for Use of Military Force implicitly authorized detention of combatants captured fighting the U.S. in Afghanistan, since detaining captured fighters to prevent their return to battle is a fundamental and universally recognized incident of waging war. It held that citizenship does not bar such detention, relying on Ex parte Quirin, and that Ex parte Milligan does not control because Milligan was not himself a prisoner of war. Applying the Mathews v. Eldridge balancing test, the plurality found that Hamdi's fundamental liberty interest in avoiding wrongful detention, weighed against the government's interest in fighting the war and avoiding burdensome litigation, requires that a citizen-detainee receive notice of the factual basis for his classification and a fair opportunity to rebut the government's evidence before a neutral decisionmaker, though hearsay and a rebuttable presumption favoring the government's evidence may be permitted. The plurality rejected the government's proposed "some evidence" standard, which would let courts merely rubber-stamp the executive's own determination without any challenge from the detainee, because that standard has traditionally been used to review records developed after adversarial proceedings, not to substitute for any proceeding at all. The plurality also responded directly to Justice Scalia's reliance on Milligan and the New York War of 1812 false-imprisonment cases, explaining that Quirin already rejected that reading of Milligan and that Scalia's approach ignores that the case involves a citizen captured on a foreign battlefield, which would create a perverse incentive for the military to detain citizens abroad rather than at home.

Dissent reasoning

Justice Scalia, joined by Justice Stevens, argued that American constitutional tradition offers only two lawful options for a citizen accused of fighting against the country: prosecute him for treason or another crime in ordinary courts, or have Congress suspend the writ of habeas corpus during rebellion or invasion. He traced this rule through the Habeas Corpus Act of 1679, the Founders' writings, War of 1812-era cases, and Ex parte Milligan, and argued that the AUMF is not a suspension of the writ and does not authorize citizen detention with sufficient clarity. He accused the plurality of inventing an unprecedented hybrid procedure under the Due Process Clause that has no basis in the Constitution or common law, and of improperly using habeas courts to supply process the executive never provided, calling this a "Mr. Fix-it Mentality" that oversteps the judiciary's role. He concluded Hamdi was entitled to release unless promptly charged or unless Congress suspends the writ. Justice Thomas dissented separately, arguing that the executive's national security and war-power determinations, including its determination that Hamdi is an enemy combatant, are entitled to near-total deference and are not properly subject to judicial second-guessing, given the courts' lack of institutional expertise in these matters. He contended the AUMF and the President's own Commander-in-Chief authority already support Hamdi's detention, that Mathews v. Eldridge is the wrong framework for weighing war powers against liberty, and that even under that framework the plurality understated the government's compelling interest in national security and intelligence-gathering while overstating the judiciary's competence to assess battlefield determinations. He would have affirmed the Fourth Circuit's judgment upholding Hamdi's detention without further process.