Klaxon Doctrine is a principle of conflict of laws which say that a federal court exercising diversity jurisdiction must apply the choice-of-law rules of the state where the court sits. The standard was set in Klaxon Co. v. Stentor Elec. Mfg. Co., 313 U.S. 487 (U.S. 1941) where the Supreme Court extended the Erie principle to conflicts questions, and required federal diversity courts to administer the conflicts law of the states in which they were sitting (“forum states”). Erie principle is the decision of the U.S. Supreme Court in Erie R.R. v. Tompkins, 304 U.S. 64 (U.S. 1938) which held that there was no federal general common law, and that except in matters governed by the U.S. Constitution or by acts of Congress, the law to be applied by the federal courts in diversity cases was the law of the state. Therefore this doctrine is also known as Erie/Klaxon doctrine.