Marrese (P) was denied membership in the American Academy of Orthopaedic Surgeons (D). P sued in state court, and his complaint was dismissed for failure to state a cause of action. P then a federal antitrust action. D filed a motion to dismiss arguing that the state claim and its dismissal precluded the federal antitrust claim. The District Court denied that motion because the state court lacked jurisdiction over federal antitrust claims. A Court of Appeals plurality held that claim preclusion barred the federal antitrust suit: a state court judgment bars the subsequent filing of a federal antitrust claim if the plaintiff could have brought a state antitrust claim under a state statute 'materially identical' to the Sherman Act. The Supreme Court granted certiorari.