Also known as the
Smith Act, the
Alien Registration Act of
1940 made it illegal to advocate or belong to a group that advocated the overthrow of the
United States government. This law was the basis of the
prosecution of many members of the
Communist and
Socialist Workers parties.
In 1957 the U.S. Supreme Court restricted the application of the law to instances of active participation in, or verbal encouragement of, specific insurrectionary activities.
Source: The Columbia Encyclopedia, Sixth Edition