Marysville Joint Unified School District v. John HR Doe, et al.

Federal common law governs the claim preclusive effect of federal court judgments. In Semtek International Inc. v. Lockheed Martin Corp., 531 U.S. 497 (2001), this Court held that, in diversity cases, federal common law incorporates the claim preclusion rules of the state where the federal court sits—and thus Federal Rule of Civil Procedure 41(a)(1)(B)’s two-dismissal rule does not bar refiling in state court. Here, the California Supreme Court extended Semtek to federal question cases. It held that plaintiffs who twice voluntarily dismissed a federal question action—asserting federal claims and supplemental state-law claims—could relitigate the state-law claims in state court. While the Tennessee Supreme Court has reached the same conclusion, the Second, Ninth, and Eleventh Circuits disagree. They hold that Rule 41(a)(1)(B) informs the federal common law of res judicata and that a second voluntary dismissal of a federal question action bars relitigation of all claims, including supplemental statelaw claims. The question presented is: Whether a second voluntary dismissal of a federal question action—which Rule 41(a)(1)(B) declares “operates as an adjudication on the merits”—bars the plaintiff from relitigating supplemental state-law claims in state court under federal common law.