John Sinclair, a counterculture activist whose nearly 10-year prison sentence for sharing joints with an undercover police officer was cut short after John Lennon and Yoko Ono sang about his plight at a protest rally, died on Tuesday in Detroit. He was 82.

His publicist, Matt Lee, said the cause of his death, in a hospital, was congestive heart failure.

As the leader of the White Panther Party in the late 1960s, Sinclair spoke of assembling a “guitar army” to wage “total assault” on racists, capitalism and the criminalization of marijuana. “We are a whole new people with a whole new vision of the world,” he wrote in his book “Guitar Army” (1972), “a vision which is diametrically opposed to the blind greed and control which have driven our immediate predecessors in Euro-Amerika to try to gobble up the whole planet and turn it into one big supermarket.”

He also managed the incendiary Detroit rock band the MC5. Their lyrics — “I’m sick and tired of paying these dues/And I’m finally getting hip to the American ruse” — were a kind of ballad for the cause.

Sinclair’s command of this “raggedy horde of holy barbarians,” as he described them in his book, was upended in 1969 when Judge Robert J. Colombo of Detroit Recorder’s Court sentenced him to 9 1/2 to 10 years in prison for giving two joints to an undercover police officer.

During the hearing, Sinclair argued that he had been framed.

“Everyone who is taking part in this is guilty of violating the United States Constitution and violating my rights and everyone else that’s concerned,” he said. He added, “There is nothing just about this, there is nothing just about these courts, nothing just about these vultures over here.”

In prison, he was responsible for folding underwear but spent most of his time reading and writing. “This is the best thing that’s ever happened to me or our organization,” he told Big Fat magazine during his incarceration. Asked why, he said, “It exposes the fascists who put me here.”

Sinclair’s case became a cause célèbre in the counterculture movement. On Dec. 10, 1971, 15,000 supporters attended a rally and concert at Crisler Arena in Ann Arbor, Michigan. They brought a lot of marijuana with them.

“People were not only smoking joints openly and passing them around,” Keith Stroup, the founder of the marijuana advocacy group NORML (the National Organization for the Reform of Marijuana Laws), wrote, “but several people, including one sitting near my seat, had quantities of marijuana sitting open on their laps, freely rolling joint after joint, to make sure everyone who attended could get high for the occasion.”

Sinclair spoke to the audience from prison over a phone line connected to the arena’s speaker system. “Say something to me,” he said, and the crowd shouted, “Free John!”

Among the musicians who performed were Stevie Wonder and Bob Seger. Allen Ginsberg and Abbie Hoffman spoke, along with Bobby Seale, a founder of the Black Panther Party. The event was supposed to end at midnight, but it kept going, and at around 3 a.m. Lennon and Ono appeared onstage. The audience went berserk.

With anti-war activist Jerry Rubin playing drum in the background, Lennon and Ono performed a song they had written for Sinclair. It began:

It ain’t fair, John Sinclair

In the stir for breathin’ air

Won’t you care for John Sinclair?

In the stir for breathin’ air

Let him be, set him free

Let him be like you and me.

A few days later, the Michigan Supreme Court announced that it was reviewing the case. Sinclair was released on bond. The court later overturned the conviction.

Justice John B. Swainson held that Sinclair had been entrapped by Detroit police officers. Two other justices, Thomas E. Brennan and Paul L. Adams, wrote that Sinclair’s sentence was “cruel and unusual punishment in light of the case against him.”

“Today is a great victory,” Sinclair said at a news conference, puffing on a joint.

John Alexander Sinclair Jr. was born on Oct. 2, 1941, in Flint, Michigan. His father worked for Buick Motors, first on the assembly line and later in management. His mother, Elsie (Newberry) Sinclair, was a teacher. The family lived in Davison, a small town near Flint.

He graduated from the University of Michigan in 1964 with a bachelor’s degree in American literature. He pursued a master’s degree in English literature at Wayne State University in Detroit, but he was expelled “because I was a dope fiend,” he told The Detroit Free Press.

Sinclair stayed in the city. He wrote poetry, organized jazz concerts and started an artists’ workshop with his girlfriend, Magdalene Arndt, known as Leni. They married in 1965 and became active in the local counterculture movement. With his friend Pun Plamondon, they started the White Panther Party in 1968.

“We thought,” Sinclair wrote in “Guitar Army,” “that political organization and political theory were things of the past which had no relevance to the contemporary situation, that whatever happened would have to happen spontaneously if it was going to mean anything at all, and that all we had to do was to keep pumping out our propaganda as hard as we could and then just wait for the right moment to present itself, at which time there would be a huge apocalyptic flash and the future of the world would be settled in a matter of days.”

But in a matter of months, Sinclair was in prison. While there, he was indicted along with Plamondon and another White Panther Party member on charges that they had conspired in 1968 to bomb a CIA recruiting office in Ann Arbor. The case against them was built on wiretaps for which the FBI had not obtained warrants, and it collapsed after the U.S. Supreme Court ruled that the wiretaps were unconstitutional.

John and Leni Sinclair divorced in 1978. He married Patricia Brown in 1989. She survives him, along with two daughters from his first marriage, Celia and Sunny Sinclair; three stepdaughters, Krishna Tyson, Chonita Robinson and Kenya Makeba Carr; a sister, Kathleen Sinclair-Smith; and a granddaughter.

After his legal problems ended, Sinclair settled into a life of advocacy, writing poetry and articles for alternative newspapers and producing music festivals. He smoked marijuana every day. After Michigan legalized it in 2018, Sinclair was among the first customers in line when it became available for purchase.

“Things have come full circle, haven’t they, John?” someone in line asked him, according to MLive, a Michigan news outlet. Sinclair replied, “It would be more full if they came and gave me back the weed that they took.”

The New York Times News Service