Accusing Mayor Rahm Emanuel of trying to cut a “back-room deal” with U.S. Attorney General Jeff Sessions, lawyers for Black Lives Matter Chicago and other community groups filed a class-action lawsuit Wednesday seeking federal oversight of the city’s police department.

The 132-page complaint immediately blew up the debate over police reform in Chicago. It may force City Hall to the negotiating table after the mayor tried to abandon the idea of a federal monitor. Or, it may lead to a lengthy court battle.

Six individuals and seven community groups are named as plaintiffs in the lawsuit, which was brought on behalf of people who “have been, or in the future will be, subjected to use of force by the CPD.” It also targets 15 police officers, as well as the city.

“CPD officers abide by an ingrained code of silence and ‘warrior mentality’ wholly disconnected from the policies that exist on the books,” the plaintiffs’ lawyers wrote in the complaint. “The ‘thin blue line’ reigns supreme. The city of Chicago has proven time and time again that it is incapable of ending its own regime of terror, brutality and discriminatory policing.”

The case has been assigned to U.S. District Judge John Z. Lee, and a hearing date has been set for June 21.

Chicago Corporation Counsel Edward Siskel and Police Supt. Eddie Johnson insisted Wednesday the city wanted to take a different path toward the same reforms. Fraternal Order of Police President Kevin Graham promised to “oppose the imposition of policies backed by this movement in every instance.”

The lawsuit was filed five months after the Justice Department announced it had found widespread constitutional violations by the Chicago Police Department.

Emanuel has recently backed off his pledge to seek federal oversight of the police department, announcing plans to have an independent monitor oversee reforms instead. Illinois Attorney General Lisa Madigan has joined in the public push-back, and Emanuel has refused to respond to pressure from her office.

The complaint, filed early Wednesday, details the police department’s troubled history, reaching all the way back to the “shoot to kill” orders during the 1968 Democratic National Convention and CPD’s 1969 execution of Black Panther leader Fred Hampton.

It also accuses individual officers of excessive force against the plaintiffs. For example, Chante Linwood claimed police assaulted her after she was turned away from a Gold Coast nightclub in April 2016.

“Two officers came over and, before I knew it, I was slammed into the side of the building,” Linwood told reporters. “My hair was pulled and I was shoved to the ground. The officers put their knees on my back and yanked my shoulders from my back to handcuff me. I couldn’t lift my arms for days afterward.”

Linwood said she was pregnant with her youngest child at the time.