 The Smith Act trials of Communist Party leaders were a series of federal prosecutions conducted from 1949 to 1958 in which leaders of the Communist Party of the United States ( CPUSA ) were accused of violating the Smith Act , a statute which imposed penalties on those who advocated violent overthrow of the government . The prosecution argued that the CPUSA 's policies promoted violent revolution ; the defendants countered that they advocated a peaceful transition to socialism , and that the First Amendment 's guarantee of freedom of speech and of association protected their membership of a political party . The trials led to the US Supreme Court decisions Dennis v. United States ( 1951 ) and Yates v. United States ( 1957 ) . 
