Mandel gained mainstream attention in the United States following the rejection of his visa by Attorney General John N. Mitchell against the suggestion of Secretary of State William P. Rogers in 1969. Attorney General Mitchell acted under the Immigration and Nationality Act of 1952 (also known as the McCarran–Walter Act). This act states that those who "advocate the economic, international and governmental doctrines of world Communism" and "who write or public any written or printed matter advocating or teaching the economic international and governmental doctrines of world Communism" can have their visas barred. Mandel had been granted visas in 1962 and 1968 but had violated the conditions of his second visit unknowingly by asking for donations for the defence in the legal cases of French demonstrators. As a result of his rejected visa, a number of American scholars came out to vouch for his right to visit the United States. They attempted to highlight that he did not affiliate with the Communist Party and had publicly spoken out against the invasion of Czechoslovakia in 1968.
