U.S. federal law passed in 1940 that made it a criminal offense to advocate violent overthrow of the government or to organize or be a member of any group or society devoted to such advocacy. After World War II this statute was made the basis of a series of prosecutions against leaders of the Communist Party and the Socialist Workers Party. The conviction of the principal officers was sustained, and the constitutionality of the “advocacy” provision upheld, by the Supreme Court in Dennis v. United States (1951); but in a later case (Yates v. United States, 1957) the court offset this position somewhat by a strict reading of the language of the Smith Act, construing “advocacy” to mean only urging that includes incitement to unlawful action.