In September 1950 Congress passed the Internal Security Act over President Harry S Truman’s veto. This act is also known as the McCarran Act, for its sponsor, Senator Pat McCarran of Nevada. The act required that Communists and Communist-front organizations register with the U.S. government. The law allowed the U.S. government to arrest suspected subversives, or people trying to overthrow the government, and to jail registered Communists during national emergencies. It prohibited Communists from holding national defense jobs. It also allowed the government to deny U.S citizens who were Communists passports for international travel. The acts also forbade anyone who had been a member of a totalitarian organization from entering the United States. On March 28, 1951, Congress amended the act. It became illegal for the government to keep out of the country anyone who had joined a subversive group under the age of 16 or to maintain their livelihood. The 1964 U.S. Supreme Court case Aptheker v. Secretary of State further weakened the Internal Security Act by limiting the government’s ability to forbid U.S citizens’ international travel.
