See Petite v. United States, 361 U.S. 529 (1960). The Justice Department policy of refusing to bring a federal prosecution following a state prosecution except when necessary to advance compelling interests of federal law enforcement. A Department of Justice internal rule that forbids a federal prosecution based on a previous state or federal prosecution on the same acts unless approved by the Assistant Attorney General, there is a substantial federal interest, the prior prosecution failed to vindicate the federal interest, and there is evidence to sustain a conviction.