Opinion of the Court
This Court granted Cruz’s petition for certiorari, 596 U. S. ___ (2022), limited to the question whether the Arizona Supreme Court’s holding that Rule 32.1(g) precluded postconviction relief is an adequate and independent state-law ground for the judgment.
II
“This Court will not take up a question of federal law in a case ‘if the decision of [the state] court rests on a state law ground that is independent of the federal question and adequate to support the judgment.’ ” See Lee v. Kemna, 534 U. S. 362, 375 (2002) (quoting Coleman v. Thompson, 501 U. S. 722, 729 (1991) (emphasis added in Kemna)). Here the Court focuses on the second of these requirements: adequacy.
“The question whether a state procedural ruling is adequate is itself a question of federal law.” Beard v. Kindler, 558 U. S. 53, 60 (2009). Ordinarily, a violation of a state procedural rule that is “ ‘firmly established and regularly followed’ … will be adequate to foreclose review of a federal claim.” Lee, 534 U. S., at 376. Nevertheless, in “exceptional cases,” a “generally sound rule” may be applied in a way that “renders the state ground inadequate to stop consideration of a federal question.” Ibid. This is one of those exceptional cases.
In particular, this case implicates this Court’s rule, reserved for the rarest of situations, that “an unforeseeable and unsupported state-court decision on a question of state procedure does not constitute an adequate ground to preclude this Court’s review of a federal question.” Bouie v. City of Columbia, 378 U. S. 347, 354 (1964). “Novelty in procedural requirements cannot be permitted to thwart review in this Court applied for by those who, in justified reliance upon prior decisions, seek vindication in state courts of their federal constitutional rights.” NAACP v. Alabama ex rel. Patterson, 357 U. S. 449, 457 (1958). This Court has
