Neil Young performs at the Harvest the Hope concert in Neligh, Neb. on Saturday, Sept. 27, 2014. The concert in northeast Nebraska was organized to raise money for efforts opposing the Keystone petroleum pipeline. (AP Photo/Dave Weaver)

The New York City transit authority has a rule that expressly allows people to play music beneath the streets.

So why did a cop arrest a busker over the weekend after he refused to stop singing and playing his acoustic guitar on a subway platform?

At the busker’s urging, the officer first read out loud the relevant section of the MTA rulebook, noting that “artistic performances, including the acceptance of donations,” are permitted.

Then he arrested the singer, slamming his guitar into the wall. In a video of the incident captured by a bystander, the musician sings Neil Young’s anti-authoritarian anthem “Ohio” as the officer and several backups handcuff him and drag him away. The crowd on the platform erupts into a chant of “Fuck the police.”

A police spokesperson told HuffPost in an email that the video is "under review,” but didn’t answer questions about the reasons for the arrest. The singer, Andrew Kalleen, 30, told HuffPost the arresting officer charged him with loitering, but only after poring over a law book in the back of the police van.

While state law prohibits people from loitering in the subway “for the purpose of soliciting or engaging in business,” that law seems to contradict the MTA rule, which allows performing for money.

Matthew Christian, a street violinist who co-founded BUSK-NY, a group that advocates for street performers, said the police often charge performers with vague offenses like loitering when they can’t find a more convincing justification for arrest.

“This happens so often,” Christian said. “When police officers don’t precisely know the law, they arrest someone over their own refusal to back down, and once the person is brought to the police station and booked, they can’t find anything else to charge them with, so they go mining.”

The arrest may be the latest example of a broader police crackdown on small-time hustles like panhandling and dancing in subway cars. In March, the police commissioner, Bill Bratton, proudly announced that arrests of subway peddlers and panhandlers had tripled under his watch.

“If you take care of the little things, then you can prevent a lot of the big things,” Bratton said at the time, expressing the conviction at the core of the “broken windows” strategy that he famously embraced during his first stint as New York’s top cop in the '90s.

Critics of the broken windows theory point out that no one has conclusively proves it works, and they argue that a hard-nosed approach to minor offenses only leads to violent encounters, racially biased policing, and wrongful arrests. In July, the strategy came under heightened scrutiny after Eric Garner, a Staten Island grandfather, died at the hands of police. An officer had grabbed him in a banned chokehold while attempting to arrest him for the sale of loose cigarettes.

Kalleen said police have stopped him at least five times for performing in the subway station, and he has filed a complaint against them with the Civilian Complaint Review Board, an agency that investigates allegations of police abuse. He plans to sue the department over the latest arrest.

He spent Friday night in a police holding cell, but he doesn’t sound bitter about it. At the precinct, he said, he thanked his arresting officer and another cop for risking their lives to protect people, and told them about something that happened to his family a decade ago in Northern California: A masked intruder entered their home with a shotgun and struggled with his father before the police arrived and took the man away.

After he shared that story, he said, the cops warmed up to him.

“From that point on, we were able to have a real conversation. Both cops agreed that the system is very broken. Their bosses tell them it’s their job to go out and write tickets. It’s a revenue system. We all agreed that we want it to change, but they’re doing what they’re told.”

Kalleen said he later asked his arresting officer if he liked music. “It turns out that he plays guitar too, or he used to. We talked about music that we like, and there were some bands that crossed over: Jimi Hendrix, Led Zeppelin. He’d recently gone to see Robert Plant."