NEW YORK, NY.- Leon Wildes, a New York immigration lawyer who successfully fought the U.S. government’s attempt to deport John Lennon, died Monday in Manhattan. He was 90.

His death, at Lenox Hill Hospital, was confirmed by his son Michael.

For more than three years, from early 1972 to the fall of 1975, Wildes doggedly battled the targeting by the Nixon administration and immigration officials of Lennon, a former Beatle, and his wife, Yoko Ono, marshaling a series of legal arguments that exposed both political chicanery and a hidden U.S. immigration policy.

Uncovering secret records through the Freedom of Information Act, he showed that immigration officials, in practice, can exercise wide discretion in whom they choose to deport, a revelation that continues to resonate in immigration law. And he revealed that Lennon, an anti-war activist and a vocal critic of President Richard Nixon’s, had been singled out by the White House for political reasons.

Wildes was ultimately vindicated by the stinging decision of a federal appeals court in October 1975, which said that “the courts will not condone selective deportation based upon secret political grounds” and which halted the effort to kick Lennon out of the country.

The Beatles had broken up in 1970, and Lennon and Ono moved to New York the next year. Lennon had been convicted of marijuana possession in London in 1968; that record would normally have barred him from entry, but he had obtained a waiver. The waiver was coming to an end, and the Lennons received a deportation notice.

“It was a very frightening moment,” Ono said in the 2007 documentary “The U.S. vs. John Lennon.”

When the Lennons engaged Wildes to represent them, he had barely heard of his famous clients. In his book about the case, “John Lennon vs. the USA,” published by the American Bar Association in 2016, he wrote that he was vaguely aware of the Beatles — it was nearly impossible not to be — but that the names of its members had escaped him.

“I think it was Jack Lemmon and Yoko Moto,” he recalled telling his wife after meeting them in their apartment on Bank Street in Greenwich Village. She quickly corrected him.

In the 2007 film, Lennon is seen telling reporters about Wildes: “He’s not a radical lawyer. He’s not William Kunstler.”

Lennon had publicly opposed the Vietnam War — he recorded the anti-war anthem “Give Peace a Chance” in 1969 — and he had been involved in protests on behalf of figures in the New Left movement, which campaigned against the war.

Nixon administration officials feared that he had outsize influence among the young, who would be allowed to vote in greater numbers in the 1972 presidential election, the first after the voting age had been lowered to 18 from 21. In the paranoid atmosphere then prevailing in the White House, that was enough for administration officials and their allies, notably conservative South Carolina Sen. Strom Thurmond, to go after Lennon.

Their case centered on the London marijuana conviction. But the appellate court judge, Irving Kaufman, ultimately ruled that the crime was insufficient to make Lennon an “excludable alien.”

The real reasons for the quixotic pursuit of Lennon, Wildes argued, lay elsewhere, as he was able to show thanks to his relentless digging through records. Early in 1972, Thurmond had drafted a letter recommending that Lennon be thrown out of the country, which Attorney General John Mitchell forwarded to the Immigration and Naturalization Service, the agency then in charge of visas. Of particular concern was the fact that Lennon had performed at a rally in support of a New Left figure, poet John Sinclair, who had been jailed on a marijuana charge.

“If Lennon’s visa is terminated it would be a strategic countermeasure,” Thurmond wrote.

Ten days later, “a telegram went out to all immigration offices in the United States instructing that the Lennons should not be given any extensions of their time to visit the United States,” Wildes wrote in his book.

For the next three years, the government continued to press its case, in efforts that appeared increasingly ham-fisted as public support for Lennon and Ono grew. In letters and testimony, many of the era’s cultural celebrities spoke up for them, including Bob Dylan, Joan Baez, Leonard Bernstein, artist Jasper Johns, and authors John Updike, Joyce Carol Oates and Joseph Heller, as well as New York Mayor John Lindsay.

“The sole reason for deporting the Lennons was President Nixon’s desire to remove John and Yoko from the country before the 1972 election and a new, much younger electorate getting the vote,” Wildes wrote. “To ensure his grip on power, any ‘dirty tricks,’ including the abusive misuse of the immigration process, were acceptable.”

The whole time, the FBI was keeping a close watch on Lennon. “Surveillance reports on him ran to literally hundreds of pages,” Wildes wrote.

When Lennon learned of the skulduggery, he was infuriated. “They’re even changing their own rules because we’re peaceniks,” he said in a television interview.

The 1975 ruling allowed him to remain in the country. He was killed five years later in front of the Dakota, the Upper West Side building where he and Ono lived.

In another breakthrough, Wildes found that immigration officials had the discretion to deport or not, depending on whether there were extenuating circumstances. The revelation of this policy continues to aid immigration lawyers battling the deportation of noncitizens today.

“As part of his legal strategy, Wildes conducted groundbreaking research on the ‘nonpriority’ program, and eventually filed an application for ‘nonpriority status’ for Lennon,” immigration expert Shoba Sivaprasad Wadhia wrote in her 2015 book, “Beyond Deportation.” “Wildes learned that INS had for many years been granting ‘nonpriority’ status to prevent the deportation of noncitizens with sympathetic cases, but INS had never publicized the practice.”

Throughout what Wildes acknowledged was the all-consuming job of representing the Lennons, he kept a bemused and friendly eye on his famous clients, sometimes encountering them, as others did, in what he called the “wonderful upright bed” in their Bank Street apartment.

“One could meet half the world around that bed,” he wrote — “radical types like Jerry Rubin or Bobby Seale, oddball musicians like David Peel, poets like Allen Ginsberg, actors like Peter Boyle, television personalities like Geraldo Rivera, or even political operatives like the deputy mayor of New York.”

Leon Wildes was born March 4, 1933, in Olyphant, Pennsylvania, a small coal-mining town near Scranton. His father, Harry, was a clothing and dry goods merchant, and his mother, Sarah (Rudin) Wildes, worked in his store. Wildes was educated at public schools in Olyphant and earned a bachelor’s degree from Yeshiva University in 1954 and a law degree from New York University in 1958.

He quickly gravitated toward immigration law, working for the Hebrew Immigrant Aid Society, a refugee aid organization, and helping two Americans who had gone to Israel establish their U.S. citizenship. He founded the immigration law firm Wildes & Weinberg in 1960 and went on to write numerous law review articles on immigration law and to teach at the Benjamin N. Cardozo School of Law at Yeshiva University.

In addition to his son Michael, he is survived by another son, Mark; his wife, Alice Goldberg Wiles; eight grandchildren; and five great-grandchildren.

Immigration law had “biblical import to him,” Michael Wildes, also a lawyer, recalled in a phone interview. “My father drew value from helping others achieve their American dream, as he had done — the golden grail of a green card, or citizenship.”

This article originally appeared in The New York Times.