Protests against the Vietnam War had escalated significantly following the announcement of the Cambodia invasion on April 30, 1970, and the shooting deaths of four student protestors at Kent State just four days later. Many such gatherings would feature peaceful demonstrators singing Lennon's 1969 anthem "Give Peace A Chance," but others were more threatening. Newly relocated to New York City, John Lennon began to associate publicly with such radical figures as Abbie Hoffman, Jerry Rubin and Bobby Seale, and the White House reportedly grew concerned, according to the 2006 documentary The U.S. vs. John Lennon, over his potentially powerful influence with a generation of 18-to-20-year-olds who would be allowed, for the very first time, to vote in the 1972 presidential election. "I suppose if you were going to list your enemies and decide who is most dangerous," Walter Cronkite would later say, "if I were Nixon, I would put Lennon up near the top."
South Carolina Senator Strom Thurmond was of the same opinion, and it was a letter he wrote to the White House in his capacity as Chairman of the Senate Internal Security Committee that prompted the White House to action. An FBI investigation of Lennon turned up no evidence of involvement in illegal activities, but the matter was referred nonetheless to the Immigration and Naturalization Service, which began deportation proceedings against Lennon and his wife, Yoko Ono, on the basis of a 1968 marijuana conviction in England.
Leon Wildes, the immigration attorney who would handle Lennon's case over the next four-plus years, would say of his client's reaction to the case, "He understood that what was being done to him was wrong. It was an abuse of the law, and he was willing to stand up and try to show it—to shine the big light on it." Lennon's persistence in fighting the case finally paid off on October 7, 1975, with a court decision that left no question as to the real motives behind the deportation: "The courts will not condone selective deportation based upon secret political grounds," wrote Judge Irving Kaufman, who also went on to say, "Lennon's four-year battle to remain in our country is testimony to his faith in this American dream."
Less than one year later, in June 1976, John Lennon got his green card.