Jillian and I were talking about this in another thread. There are a number of cases in the various circuits, but I'll stick to the Supreme Court decisions. Bradford Electric Light Co. v. Clapper 286 U.S. 145 (1932) This is still the leading example case of its type according to the Horn Book on the subject. In a dispute between Vermont and New Hampshire, the Court "recognized tthat a court might refuse to enforce a foreign cause of action if obnoxious to its policy..." By foreign they meant another state. Pacific Employers Inc. Co. v. Industrial Accident Commission 306 U.S. 493 (1939) "While the Court examined the conflicting interests of the states, it simply held that the Full Faith and Credit Clause did not require a state to ignore its policy to enforce another state's statute." In a later case citing to Pacific, in 1955, the Court noted that it had, in Pacific, "recognized that Full Faith and Credit did not require application of a foreign statute that conflicts with the policy of the forum." Again, by 'foreign' they were referring to another state. Nevada v. Hall 440 U.S. 410 (1979) the Court held that California could refuse to give Full Faith and Credit to a Nevada act under the reasoning that the Nevada act was "obnoxious" to the policies of California.