Henry Montgomery received mandatory life without parole for a murder he committed at age seventeen, and Louisiana courts rejected his collateral challenge because they treated the rule in Miller as nonretroactive. The Supreme Court held that it had jurisdiction to decide whether Miller applies retroactively in state collateral proceedings. It held that Miller announced a substantive Eighth Amendment rule that applies retroactively: life without parole remains possible for the rare juvenile whose crime reflects irreparable corruption, but a juvenile whose crime reflects transient immaturity must have a chance to show that fact. The Court reversed the Louisiana Supreme Court’s judgment and remanded for proceedings consistent with Miller; a state may remedy a violation by providing parole eligibility rather than resentencing. Justice Scalia, joined by Justices Thomas and Alito, dissented, and Justice Thomas filed a separate dissent.