Federal Courts: Conflict of Laws: Duty of Federal Court to Apply State Conflict of Laws Rules

In a suit on a contract brought in the United States District Court in Delaware, based on diversity of citizenship, the court allowed interest costs on the basis of the Civil Practice Act of New York where the contract was made. The Circuit Court of Appeals for the Third Circuit affirmed the ruling upon the ground that it was the best rule, without regard to the Delaware conflicts law. On certiorari, held reversed, on the ground that the doctrine of Erie Railroad v. Tompkins prohibits such an independent determination by the federal court of conflict of laws rules. Klaxon Co. v. Stentor Electric Mfg. Co., (U.S. 1941) 61 S. Ct. 1020.