On March 1, 1972, the FBI had John Lennon and Yoko Ono in its sights.

A federal agent declared that the superstar couple would be arrested for “interstate travel in the furtherance of conspiracy to incite a riot” if they dared to attend the Republican National Convention in Miami that year.

Writes lawyer Leon Wildes: “I had never seen the government so determined to remove anyone from the United States.”

Wildes’ book tells the story of the Nixon administration’s battle to deport Lennon, ostensibly for a prior conviction in the UK for hashish possession. The real reason? The government feared that Lennon’s outspoken stance against the Vietnam War and other political beliefs threatened to influence the country’s 18-to-20-year-olds in the 1972 election, just as the national voting age had been lowered.

Whether or not Lennon and Ono were planning to attend the RNC that year is unclear, but they were definitely politically active.

The Beatle and his wife moved from London to Greenwich Village on a temporary visa after Lennon’s drug arrest in 1968. They participated in demonstrations, including a December 1971 rally for the release of MC5 band manager John Sinclair, who was serving 10 years for selling two marijuana joints to an undercover police officer.

In front of 15,000 people in Michigan, Lennon performed a song he wrote for the occasion called “John Sinclair” and talked to the crowd about the importance of staying involved. Sinclair, who had already served two years, was freed by week’s end.

This made the federal government very nervous.

According to Wildes, Sinclair was involved, via the White Panther Party, in “obtaining guns and dynamite, blowing up the CIA office in Ann Arbor and laying plans for guerrilla actions in northern Michigan.”

While there was no proof Lennon was aware of this, South Carolina Sen. Strom Thurmond drafted a memo to US Attorney General John Mitchell, who oversaw the Immigration and Naturalization Service, spelling out the danger in Lennon’s new friendships.

Noting the Chicago Seven “devised a plan to hold rock concerts in various primary election states . . . to recruit persons to come to [the RNC] in August 1972,” he said they “intend to use John Lennon as a drawing card to promote their success.” Mitchell acted immediately, and Lennon’s visa was revoked days later, beginning the deportation process.

Wildes, an immigration attorney with an office on Madison Avenue, was referred to Lennon by an old law-school classmate. When he arrived at the couple’s Bank Street home, Lennon explained how much he loved living in the States: “Everything in our world — we’re artists, you know — now comes up in the USA. It’s like the time of the Impressionist artists, when everything took place in Paris, or in early Rome. It’s all here now. This is where it’s at, and we’d love to be here. We just understand that it can’t be arranged.”

Wildes had looked up the statute regarding immigration and marijuana and found that the government could exclude people from the US “who have been convicted of any law or regulation to the illicit possession of . . . narcotic drugs or marijuana.”

His own research indicated that hashish was, technically, neither.

Wildes contacted Sol Marks, the INS district director for New York. The lawyer explained the situation and requested a six-month extension for the couple. A day later, Marks called Wildes back and told him he could only grant a one-month extension. What he said next sounded downright sinister. “‘These people will never get another extension . . . Leon, tell them to get out!’ ”

When that didn’t happen, “the Nixon administration made life intolerable for John Lennon and Yoko Ono,” Wildes writes.

“Alleged phone repairmen came to ‘check’ the Lennons’ telephone but left promptly when ID was requested,” Wildes writes. “Two men, stationed just across Bank Street, seemed to be fixing a bike interminably. When John and Yoko got into an automobile, the same two men appeared in a car behind them, making certain the Lennons knew they were being followed.” It got so bad that Lennon began using a woman’s voice when calling Wildes by phone.

The stress of the four-year intimidation almost destroyed the couple. Their infamous split — when Lennon spent 18 months in LA, mostly drunk — occurred during this time.

Still, the couple did an admirable job of maintaining their poise.

Early in the case, when they were introduced to the prosecuting attorney for the INS, Vincent Schiano, Lennon “jumped to his feet, whipped out a handkerchief from his pocket, bent down and started polishing Schiano’s shoes! He looked up with a grin and asked, ‘Is there anything else I could do for you, Mr. Schiano?’ ”

Finally, after four years of legal tussling, Lennon was granted permanent resident status thanks to a technicality regarding his UK conviction. (Ono had already won the same status.)

By then, of course, Nixon had left office. But Lennon’s love of his adopted homeland — and especially his chosen hometown of New York City — had not wavered.

“Throughout his fight to stay in the United States, he felt most welcomed by New Yorkers,” Wildes writes. “Lennon’s four-year battle to remain in our country is testimony to his faith in this American dream.”