Tompkins was injured by an object protruding from a train as he walked beside the tracks in PA. He brought a New York action under diversity.
Questions of law
What law does a federal court apply? Does U.S.C. 1652 apply only to statute or to common law as well? Under Swift, the federal court sitting in diversity applies only state statutes, not state common law. The railroad argued that PA precedent regards persons walking beside tracks as trespassers and permits recovery only for wanton negligence. Thompkins argued the question should be decided under federal common law under Swift.
In a landmark decision, the Court overruled Swift, holding that the creation of a federal common law over state common law was unconstitutional judicial overreach and denied equal protection. It remanded to the trial court for a decision based on state common law.