CHICAGO >> Mayor Rahm Emanuel has taken his fight against President Donald Trump’s immigration policies to court, with Chicago becoming one of the first cities today to sue over what many U.S. cities argue are illegal bids to withhold public safety grants from so-called sanctuary cities.

A 46-page lawsuit against the government was filed in U.S. District Court in Chicago a day after Emanuel announced the litigation and said the city won’t “be blackmailed” into changing its values as a city welcoming of immigrants.

It’s the latest round in a battle pitting several U.S. cities against the Trump administration. The cities have opted to limit cooperation with government enforcement of immigration law while federal officials threaten to withhold funding if those cities don’t comply.

The first order of business now that Chicago’s suit has been filed will be to ask a judge to put a freeze on the policy as the civil case plays out, said Edward Siskel, the head of City Hall’s legal department. That request for a preliminary injunction could be made within days.

Chicago has received the grant funds at the heart of the lawsuit since 2005. It spent $33 million in grants to buy nearly 1,000 police cars in that 12-year period; it got $2.3 million last year. In addition to cars, funds were also used for radios and SWAT equipment.

While the grant money amounts to a fraction of Chicago’s public safety budget, Emanuel has said fighting the government now could help prevent the withholding of more money later. He described the Trump measures so far as just “the camel’s nose under the tent.”

Chicago’s suit focuses on new conditions set by Attorney General Jeff Sessions for cities to qualify for grant money. They include the sharing immigration-status records with federal agencies, providing 48-hours notice of a detainee’s release if immigration violations are suspected and giving federal agents unfettered access to jails.

“The government,” the lawsuit says, can’t “unilaterally” set new conditions that weren’t approved by Congress “and that would federalize local jails and police stations, mandate warrantless detentions in order to investigate for federal civil infractions, sow fear in local immigrant communities, and ultimately make the people of Chicago less safe.”

Chicago’s sanctuary policies date back to the mid-1980s and successive city councils have confirmed or expanded the protections.

The city prohibits police from providing federal Immigration and Customs officials access to people in police custody, unless they are wanted on a criminal warrant or have serious criminal convictions. Local police are also barred from allowing ICE agents to use their facilities for interviews or investigations and from responding to ICE inquiries or talking to ICE officials about a person’s custody status or release date.

City authorities say the policies help encourage residents of the immigrant community to inform police when they are victims of crimes.

“If Chicago submits to the Department’s demands, it will forfeit decades’ worth of trust and goodwill that its police force has built in the communities it serves,” the new lawsuit argues. “And as those decades of experience show, that kind of trust, once lost, is lost forever.”

It also says the Trump administration’s contention that more lenient immigration policies contribute to crime “is divorced from reality.”

The lawsuit, which names Sessions, seeks to remove the immigration-related conditions for the grant applications.

When asked for comment about the lawsuit today, the Department of Justice spokesman directed The Associated Press to Sessions’ previous comments, including those saying sanctuary cities threaten safety.

A department spokesman, Ian D. Prior, did respond in an email over the weekend when Emanuel began speaking about the legal action.

“It’s especially tragic that the mayor is less concerned with that staggering figure than he is spending time and taxpayer money protecting criminal aliens and putting Chicago’s law enforcement at greater risk,” he said.

In March, the Justice Department sent letters to officials in California and major cities including New York, Chicago, Philadelphia and New Orleans, all places the Justice Department’s inspector general has identified as limiting the information local law enforcement can provide to federal immigration authorities about those in their custody.

The department warned that the administration will punish communities that refuse to cooperate with efforts to find and deport immigrants in the country illegally. But some of the localities remained defiant, despite risking the loss of funds that police agencies use to pay for everything from body cameras to bulletproof vests.