Scalia's opinion for the Court interpreted AEDPA's requirement that a federal court can only grant a habeas corpus petition to set aside a state court conviction if the conviction results in a decision "contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States." The Court ruled that "clearly established Federal law" does not include Supreme Court decisions that are announced after the last adjudication of the merits in state court but before the defendant's conviction becomes final.
Scalia dissented from the Court's denial of certiorari, of a Ninth Circuit decision that set aside two murder convictions on the finding that there was significant evidence that a jailhouse informant had lied regarding the defendant's confession. Scalia believed this evidence was circumstantial, as it regarded the informant's lying regarding other matters at the trial and in subsequent unrelated trials, which even the Ninth Circuit acknowledged did not determine that he necessarily lied regarding the confession in this trial. Scalia wrote that this evidence "might permit, but by no means compels, the conclusion that Storch [the informant] fabricated Maxwell's admission," which meant that under AEDPA the convictions should have stood because "[t]he only factual determination necessary to support the California court's decision was that Maxwell had not established that Storch lied." Scalia also took issue with the Ninth Circuit's holding that the use of false testimony violated the Fourteenth Amendment's Due Process Clause, whether or not the prosecution knew it was false. "We have never held that, and are unlikely ever to do so."
Scalia closed his opinion with a general note of criticism regarding the Ninth Circuit: "It is a regrettable reality that some federal judges like to second-guess state courts. The only way this Court can ensure observance of Congress's abridgement of their habeas power is to perform the unaccustomed task of reviewing utterly fact-bound decisions that present no disputed issues of law. We have often not shrunk from that task, which we have found particularly needful with regard to decisions of the Ninth Circuit... Today we have shrunk, letting stand a judgment that once again deprives California courts of that control over the State's administration of criminal justice which federal law assures."