Have communists been banned from immigrating to the US for decades?
Laws that restrict communists from immigrating to the U.S. have existed since the mid-20th century.
Throughout the 1940s, immigration officials had broad leeway to deny visas to immigrants they suspected might engage in anti-American sedition. In 1950, the McCarran Internal Security Act made communists, fascists and totalitarians ineligible for naturalization. And in 1952, the Immigration and Nationality Act excluded all aliens voluntarily affiliated with the Communist Party and other totalitarian groups from immigrating to the U.S.—a prohibition that continues to this day.
According to U.S. immigration authorities, any applicant "meaningfully" and voluntarily involved with the Communist Party or other suspect group (had a membership card, paid dues, gave money, advocated ideals, etc.) is not admissible to the United States.