Foreign communists, and others whose potential visits to the U.S. were considered to be not in the best interest of the United States, were prohibited entry into the country. The Subversive Activities Control Act of 1950 barred from entry into the U.S. all those who advocated ‘the economic, international and governmental doctrines of world communism or […] of any other form of totalitarianism’.

Past or present membership in the Communist Party was deemed sufficient to prohibit entry. Moreover, for purposes of this Act past membership in Nazi or fascist parties were not considered to be included under the definition of ‘totalitarian’.

(Source.)