McCarran Internal Security Act

The Internal Security Act (also known as the Subversive Activities Control Act, McCarran Act or ISA) of 1950 is a United States federal law that required the registration of Communist organizations with the Attorney General in the United States and established the Subversive Activities Control Board to investigate persons thought to be engaged in "un-American" activities. Members of these groups could not become citizens. Citizen-members could be denaturalized in five years.

It was a key institution in the era of the Cold War, tightening alien exclusion and deportation laws and allowing for the detention of dangerous, disloyal, or subversive persons in times of war or "internal security emergency". The Democratic Congress overrode President Harry S. Truman's veto to pass this bill. Truman called the bill "the greatest danger to freedom of speech, press, and assembly since the Alien and Sedition Laws of 1798."

Sections of the ISA were gradually ruled unconstitutional by the Supreme Court.

Much of the Act has been repealed, but some portions remain intact. Violation of Section 797 of Title 50, United States Code (Section 21 of "the Internal Security Act of 1950"), for example, may be punishable by a prison term of up to one year.

See also

• Communist Registration Act
• Hatch Act of 1939
• McCarran-Walter Act
• Alien Registration Act
• House Un-American Activities Committee (HUAC)
• Second Red Scare
• McCarthyism
• Internal Security Act