McCarran Internal Security Act

The Internal Security Act or McCarran Act of 1950 required communist and communist front organizations to register with the Attorney General. Members of these groups could not become citizens. Citizen-members could be denaturalized in five years. Congress overrode President Harry Truman's veto.

Sections of the ISA were gradually ruled unconstitutional by the Supreme Court and it was completely repealed in 1990.

See also:

• Alien Registration Act
• McCarthyism