A federal judge on Wednesday outlined plans to release hundreds of people who have been arrested by immigration agents in Chicago, saying that federal authorities had violated a years-old settlement that prohibited certain warrantless immigration arrests.

The arrests made national news as part of the Trump administration`s "Operation Midway Blitz," which has flooded Chicago with immigration agents who have antagonized local residents and made hundreds of arrests across the city.

U.S. District Judge Jeffrey Cummings said that federal authorities violated a 2022 settlement prohibiting arrests made without probable cause to indicate that someone is both in the United States illegally and a flight risk. The settlement is known as the Castañon Nava consent decree, after a 2018 lawsuit featuring a plaintiff of that name.

The order could apply to over 600 people - the vast majority of whom have no criminal record, plaintiffs have said - who have been arrested by immigration authorities as part of the operation. However, there are potentially thousands of people who have been arrested and could ultimately be affected by the judge`s decision. Cummings gave the government until Nov. 19 to provide plaintiffs with a list of people arrested by Immigration and Customs Enforcement or Customs and Border Protection in Chicago since June 11. Both sides of the suit have until Nov. 21 to file a status report.

The litigation over the arrests is ongoing and was brought by the National Immigrant Justice Center and the ACLU of Illinois.

"Most importantly, the court committed to enforcing our agreement with the federal government - a step that creates a pathway for even more of the hundreds of people illegally arrested and detained during Operation Midway Blitz to be released. The court is holding ICE and CBP accountable for breaking the law," Michelle Garcia, deputy legal director at the ACLU of Illinois, said in a press release Wednesday.

"At every turn, activist judges, sanctuary politicians, and violent rioters have actively tried to prevent our law enforcement officers from arresting and removing the worst of the worst," DHS spokesperson Tricia McLaughlin said in a statement. (The Trump administration is not prioritizing going after the "worst of the worst.")

"Now an ACTIVIST JUDGE is putting the lives of Americans directly at risk by ordering 615 illegal aliens be released into the community."

Justice Department attorney William Weiland said that at least 12 of the group the judge assessed on Wednesday were considered significant security risks, according to the Chicago Tribune. Cummings said those deemed threats to public safety would not be released from detention. Others may have already been removed from the United States.

"There might be quite a few of them who are already gone," Cummings said, according to the Chicago Sun-Times` Jon Seidel.

"They`re all being awarded bond ... but how is that process going to happen?" said Mark Fleming of the National Immigrant Justice Center, at a news conference after Wednesday`s hearing, CNN reported. People eligible to be released "are probably all over the country" and need to be located, he noted, since immigration detainees are regularly moved to detention centers in different states.

Cummings said he planned on allowing a $1,500 bond for those eligible for release under his order, the Tribune reported. Those released would enter ICE`s "Alternatives to Detention" program, which involves physical check-ins and location tracking via cell phone app or ankle monitor.

Weiland called the order "quite significant," the Tribune said.

While immigration officials have said some arrests are targeted, others are "collateral" - the government`s term to mean they occur incidentally, in the course of another enforcement action. Others are the result of racial profiling and random stops.

"As we`re digging into it, we are very concerned that many, if not most [of ICE arrests], are violations of our consent decree," Fleming previously told ABC 7.

"Our initial analysis is that it`s over 3,000 arrests," he added. "We`ve started to dig into the case file that they produced to us, and the vast majority are violations. If they did not have a prior order of removal, in almost all circumstances, they`ve been uniformly violating the consent decree."

He told CNN that at least 1,100 of the people who have been arrested are believed to have already left the country.

Last month, Cummings found that immigration agents had violated the settlement with the arrests of 22 people in the early days of Trump`s second term, Block Club Chicago reported.

The settlement was initially set to expire in May, the outlet noted, but the National Immigration Justice Center and the ACLU of Illinois moved earlier this year to extend it. Cummings said in a June hearing that it remained in effect.

Last month, he extended it through February, writing that "ICE lacked statutory and regulatory authority to engage in its policy of issuing I-200 warrants to collaterals in the field." I-200s are a form of administrative warrant - not signed by a judge - that ICE officers use to identify people they want to arrest pursuant to immigration proceedings. In Chicago, officers have acknowledged filling them out at the scene of a given person`s arrest.

In his ruling last month extending the settlement, Cummings said the importance of probable cause was "further heightened" by the Supreme Court`s decision to temporarily allow federal law enforcement to detain someone based on factors - according to a concurring opinion from Justice Brett Kavanaugh - including "apparent race or ethnicity," "speaking Spanish or speaking English with an accent," "the type of work one does," and "presence at particular locations such as bus stops, car washes, day laborer pickup sites, agricultural sites, and the like." (These criteria have given rise to a new term: a "Kavanaugh stop.")

The judge also stated last month that ICE officials had incorrectly informed field offices in June that the settlement no longer applied; in fact, it was still in effect, as plaintiffs were actively seeking to extend it. Cummings ordered ICE to broadcast "to all ICE officers nationwide" that the agreement was still in effect.