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The McCarran Internal Security Act

The McCarran Internal Security Act (1950)was enacted during the early Cold War years and shortly after U.S. intervention in the Korean War in response to growing domestic anti‐Communist fears. In the wake of Republican accusations that the Truman administration was not diligent enough against Communists and Communist sympathizers in the United States, a coalition of conservative Democrats and Republicans adopted the measure.

The act, named after Democratic senator Patrick A. McCarran of Nevada, required “communist‐action” and “communist front” organizations to register with the Justice Department. It also increased the statute of limitations, required registration of individuals trained in espionage, authorized the exclusion and deportation of Communists and other “subversives,” and provided for the detention of potential espionage agents and subversives whenever the president proclaimed an “internal security emergency.” President Harry S. Truman vetoed the bill, which was criticized as an abridgment of civil liberties; but the measure became law on 23 September 1950 after Congress overrode his veto. The registration measures were challenged in the courts and declared unconstitutional in the 1960s. The emergency detention provisions were repealed by Congress in 1971 during the presidency of Richard M. Nixon and the controversial Vietnam Antiwar Movement.
[See also Civil Liberties and War; Cold War: Domestic Course; Supreme Court, War, and the Military; Vietnam War: Postwar Impact.]


Earl Lathan , The Communist Controversy in Washington, 1966.
William R. Tanner and and Robert Griffith , Legislative Politics and ‘McCarthyism’: The Internal Security Act of 1950, in The Spectator, eds. Robert Griffith and Athan Theoharis, 1974.

William R. Tanner

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