Chicago mayor calls threat to withhold funds 'blackmail,' files lawsuit against DOJ A broader Trump executive order on the matter was blocked by a judge in April.

 -- When Chicago Mayor Rahm Emanuel announced plans Sunday to sue the Department of Justice, it was the latest salvo in the ongoing battle between the Trump administration and so-called sanctuary cities.

Two weeks ago, the Justice Department declared its intention to withhold grants from cities that do not comply with federal law requiring local police to share immigration-related information with federal law enforcement officials. The grants, administered by the Bureau of Justice Assistance, fund a range of state and local justice-centric programs spanning prosecution, education, planning and technology.

Sanctuary cities are jurisdictions that resist federal immigration regulations in order to protect otherwise law-abiding unauthorized residents in the U.S. These municipalities typically allow such individuals to utilize city services and often restrict local officers' ability to target people because of their immigration status or send that data to federal agents in the course of an arrest. Most sanctuary cities send this information to Immigration and Customs Enforcement if a person is affiliated with a gang or wanted for a violent crime.

At a press conference Sunday, Emanuel argued that the DOJ was asking Chicago to choose between its core values and its "fundamental principles of community policing."

"Chicago will not let our police officers become political pawns in a debate," said Emanuel.

"Chicago will not let our residents have their fundamental rights isolated and violated. And Chicago will never relinquish our status as a Welcoming City," he added, referring to the city's participation in a network of localities supporting immigrants and pro-immigration policies.

The city filed its lawsuit Monday, with Emanuel portraying the possible withholding of funds as "blackmail," according to an accompanying press release. The city noted that the funds have been used to purchase "SWAT equipment, police vehicles, radios and tasers," among other items.

Chicago's Welcoming City ordinance, parts of which originated in 2006, is in line with other sanctuary cities' allowances and protections and limits city officials' ability to inquire about a person's immigration status during unrelated business.

Furthermore, Chicago prevents federal immigration officers from using local resources except for "a legitimate law enforcement purpose that is unrelated to the enforcement of a civil immigration law."

Defenders of similar policies claim that they make cities safer, arguing that unauthorized individuals are more willing to report crimes and emergencies if they don't fear being deported.

"The City Council finds that the cooperation of all persons, both documented citizens and those without documentation status, is essential to achieve the city's goals of protecting life and property, preventing crime and resolving problems," Chicago's Welcoming City ordinance reads. "Assistance from a person, whether documented or not, who is a victim of or a witness to a crime is important to promoting the safety of all its residents."

But the Trump administration disagrees.

In the Justice Department's press release on the new grant conditions in July, Attorney General Jeff Sessions said, "So-called sanctuary policies make all of us less safe because they intentionally undermine our laws and protect illegal aliens who have committed crimes."

In January, President Donald Trump signed an executive order addressing the issue in broader terms.

In it, he declared sanctuary cities "ineligible to receive federal grants," which was met with criticism from a number of mayors.

A federal judge in California granted a preliminary injunction in April halting the order's enforcement.