Mere violation of state law doesn’t support habeas relief, violation of federal law being required.
But it is only noncompliance with federal law that renders a State’s criminal judgment susceptible to collateral attack in the federal courts. The habeas statute unambiguously provides that a federal court may issue the writ to a state prisoner “only on the ground that he is in custody in violation of the Constitution or laws or treaties of the United States.” 28 U. S. C. §2254(a). And we have repeatedly held that “‘federal habeas corpus relief does not lie for errors of state law.’” Estelle v. McGuire, 502 U. S. 62, 67 (1991) (quoting Lewis v. Jeffers, 497 U. S. 764, 780 (1990)). “[I]t is not the province of a federal habeas court to reexamine state-court determinations on state-law questions.” 502 U. S., at 67–68. But here, the panel’s opinion contained no hint that it thought the violation of Indiana law it had unearthed also entailed the infringement of any federal right. Not only did the court frame respondent’s claim as whether “the Indiana trial court considered non-statutory aggravating circumstances . . . in contravention of state law,” 593 F. 3d, at 551 (emphasis added), it also explicitly acknowledged that “[n]othing in [its] opinion prevents Indiana from adopting a rule permitting the use of non-statutory aggravators in the death sentence selection process. See Zant v. Stephens, 462 U. S. 862, 878 (1983) (permitting their use under federal law),” id., at 551–552 (citations omitted).