As New York Mayor Bill de Blasio takes high-profile steps to try to curtail abusive policing—sympathizing with protesters over Eric Garner’s death and vowing to reform the notorious Rikers Island prison—the city’s Law Department is going back to federal court to seek new authority to make mass arrests at protests.

The U.S. Court of Appeals for the Second Circuit has agreed to meet in full to reconsider an August ruling that sided with protesters and chastized the New York Police Department for the way it herded and arrested 700 Occupy protesters on the Brooklyn Bridge in fall 2011. It concluded that the cops violated the protesters' constitutional rights and the police did not have “cause” to arrest them.

“This decision will frustrate, not further, the work of police attempting to facilitate peaceful demonstrations while ensuring both the safety of demonstrators and those among whom demonstrations are staged,” the city’s rehearing brief argued.

Attorneys representing the protesters say the NYPD seeks renewed power to make mass arrests after entrapping protesters, as was the case in October 2011, when police walked calmly beside Occupy marchers from lower Manhattan onto the bridge. As a majority on the lower Appeals Court panel noted, most protesters did not hear any arrest warning from police and felt they were led by cops onto the Brooklyn Bridge to continue their march.

“This is the most significant and most defining legal case on protesters’ rights in the last 40 years, since the mass arrests of May Day 1970,” said Carl Messineo, Partnership for Civil Justice Fund legal director, which represented the protesters. “Mayor de Blasio seeks the authority to arrest today’s protesters in the same manner Mayor Bloomberg falsely arrested Occupy Wall Street protesters by the hundreds.”

“The city of New York has waged a major legal battle and expended enormous resources in this fight against the constitutional rights of Occupy Wall Street protesters who were illegally arrested on the Brooklyn Bridge in October 2011,” said Mara Verheyden-Hilliard, PCJF’s legal director. “This case was not just about vindicating the rights of those who were arrested, but ensuring that people can demonstrate peacefully without suddenly being arrested and taken to jail.”

The city’s legal briefs seeking a new hearing say the NYPD needs to make split decisions about arresting people at mass protests that do not need permits to march. It adds there is “significant coordination among this office: [the NYC Law Department’s Appeals Division] our client, the City Police Department; and the Mayor’s Office” in seeking a new federal court hearing to regain that authority.

“We are pleased that the full court has decided to hear the case,” Law Department spokeswoman Kate Ahlers said Thursday. She declined further comment. The mayor’s office did not respond to a request to comment.

The Court’s decision to rehear the case comes at an awkward time for Mayor de Blasio. New York City’s police-related politics are often shrill and brutal. After Garner’s death in Staten Island from a police chokehold, de Blasio expressed sympathy for the Garner family. De Blasio said he had to “literally train” his mixed-race son, Dante, how to handle himself with police. The city’s Patrolmens Benevolent Association’s quick response was to circulate a flyer for cops to sign requesting the mayor not attend the funeral if one of them was killed on the job.

Meanwhile, de Blasio appears to be focused on the most high-profile police issues. This week, he toured the Riker’s Island jail for the first time as mayor and vowed to support reforms, though that came as the U.S. Attorney planned to sue over prison conditions. The prison guards' union leader has mocked complaints about the jail.

On Friday, de Blasio is scheduled to meet with organizers of the Garner protests.

The city's October 6 legal brief filed with the Second Circuit argues that the NYPD should be free to arrest protesters whenever it wants, and has legal immunity for policing decisions.

“Even if it were true that some demonstrators might reasonably have concluded that they had been authorized to enter onto the Bridge—due to their distance from the bullhorn when warnings were given, the crowd noise around them during the warnings, and their observations of demonstrators ahead of them from their particular vantage point—this would not mean that those individuals had in fact received legal permssion to enter onto the roadway,” wrote Zachary Carter, corporation counsel of the city of New York. “The [qualified immunity] doctrine is designed to protect reasonable but mistaken judgments, and does not expect omniscience from officials as a condition of its application.”

PCJF legal director Verheyden-Hilliard said the NYPD simply wants to make mass arrests without notice.

“That is what the courts were ruling on,” she said, “simply the fact that police cannot mass arrest people without notice and opportunity to comply with an order; notably as here they were led and escorted out onto the bridge. So by seeking to overturn that order [the U.S. District Court ruling finding the arrests unconstitutional] New York City is seeking the power to conduct sweeping mass arrests without people having any clue that they’ve done anything wrong and are going to be arrested, and no opportunity to comply with any order that they should disperse.”

The city’s Law Department has previously issued statements that confirm Verheyden-Hilliard’s assessment.

Last January, the city agreed to pay $10.3 million to settle claims with 1,600 people who were arrested during the 2004 Republican National Convention in Manhattan. In its press release, the NYC Law Department touted that its “successes” included “defeating the plaintiffs’ request for an injunction that would have restricted the Police Department’s future actions by requiring the City to adopt guidelines on mass arrests” and “affirming police officers’ authority to make large group arrests in demonstration settings.”

Meanwhile, In Ferguson

Last week, a U.S. District Court in Missouri sided with protesters on a similar issue. Judge Carol Jackson issued a temporary restraining order blocking local police from using tear gas, smoke, pepper spray or other chemical agents without first giving a clear warning and a clear means of exit. The court also found that police cannot spontaneously go after protesters without warning—which is exactly what the NYPD is now seeking in another federal court.

The Missouri ruling came in a case brought by a coalition of local and national civil rights groups led by Advancement Project. They sued after St. Louis area police used excessive force on Ferguson protesters this August.

“The ruling sends a strong message that police acting under the Unified Command must respect the rights of protesters to demonstrate, and cannot use excessive tactics to curtail their message,” Denise Lieberman, senior attorney with Advancement Project, said. “Police overreach was exactly what people were protesting in the first place.”

Back in New York City, it is an open question what Mayor de Blasio might do to reverse course on the city's lawsuit seeking immunity when making mass arrests. The city's Law Department has a long history of fighting and winning in court against new restrictions concerning police tactics, as shown by the 2004 GOP Convention settlement. The mayor's spokesman for police affairs did not respond to AlterNet's requests for comment, but the mayor clearly has the executive authority to drop the suit if he wants to.