533 U.S. 678 (2001)
Zadvydas v. Davis is a landmark Supreme Court decision at the intersection of immigration law and constitutional due process.
Does 8 U.S.C. § 1231(a)(6) authorize the government to detain a noncitizen with a final order of removal for an indefinite period when there is no significant likelihood of removal in the reasonably foreseeable future, consistent with the Fifth Amendment's Due Process Clause?
Interpreting 8 U.S.C. § 1231(a)(6) to avoid serious constitutional concerns, the statute authorizes detention only for a period reasonably necessary to secure the noncitizen's removal. There is a presumptively reasonable six-month detention period following the removal order. After six months, if the noncitizen provides good reason to believe that there is no significant likelihood of removal in the reasonably foreseeable future, the government must respond with sufficient evidence to rebut that showing; if it cannot, the noncitizen must be released under supervision pursuant to § 1231(a)(3). Dangerousness alone does not justify continued detention absent a realistic prospect of removal.
No. Section 1231(a)(6) does not permit indefinite detention. Detention is limited to the period reasonably necessary to effect removal, presumptively up to six months. If, after six months, there is no significant likelihood of removal in the reasonably foreseeable future, the government must release the noncitizen under supervision.
Zadvydas is a foundational case on the limits of civil immigration detention. For law students, it demonstrates the power of the constitutional avoidance canon, the due process constraints on civil confinement of admitted noncitizens, and the Court's insistence that detention be closely tethered to its nonpunitive purpose. Practically, the decision created a six-month benchmark and a burden-shifting mechanism that govern post-removal-order custody reviews and habeas litigation. The case also sets up later doctrinal development: in Clark v. Martinez (2005), the Court applied the same reading of § 1231(a)(6) to inadmissible (unadmitted) noncitizens, ensuring uniform application of the statute's meaning across categories.