N.Y. Attorney General Sues N.Y.P.D. Over Protest Policing

“They did not train, they did not supervise, they did not stop officers who engaged in this misconduct,” she continued. “And they did not discipline them either. Instead, they failed the people of the City of New York.”

Ms. James, the state’s top prosecutor, has not brought charges against any of the officers involved in the protests, and neither have the police, local prosecutors nor the city Department of Investigation. She said her investigation, assigned by Gov. Andrew M. Cuomo, was a civil matter and that the problems with the police’s handling of the protests go well beyond the acts of individual officers.

But the lawsuit is an extraordinary step. Attorneys general rarely leverage their powers against entire police departments, especially in places where the mayor who appoints the department’s leaders belongs to the same political party. Mr. de Blasio and Ms. James are both Democrats, though the city’s top two police officials, Commissioner Dermot Shea and Chief of Department Terence A. Monahan, are Republicans who have supported President Trump.

Ms. James’s complaint amounted to an admonishment of Mr. de Blasio, Mr. Shea and Chief Monahan, who are named in her lawsuit. She recalled at the news conference how Mr. Shea had said that his department had executed its protest plan “flawlessly,” and the mayor had said the police’s uses of kettling to contain protesters were “justified.” (The mayor, in December, banned police from using the tactic.)

Ms. James has called for control of the Police Department to be stripped from the mayor and given to an independent panel. She said her investigation had found “an egregious abuse of police power; rampant, excessive use of force; and leadership unable and willing to stop it.”

Gideon Oliver, a civil rights lawyer who is representing several demonstrators who have filed lawsuits against the police, said the attorney general’s lawsuit built on years of efforts by civil rights lawyers to address “the city’s wildly inadequate responses to these problems that have been going on for a very long time.”

Patrick J. Lynch, the president of the Police Benevolent Association, the city’s largest police union, said the police response was a failure of the city’s leadership.