Boston Mayor Michelle Wu responds to a letter from U.S. Attorney General Pam Bondi demanding that Boston lift its sanctuary city policies, at a press conference in Boston, Massachusetts, U.S., August 19, 2025. REUTERS/Brian Snyder/File Photo
Boston Mayor Michelle Wu responds to a letter from U.S. Attorney General Pam Bondi demanding that Boston lift its sanctuary city policies, at a press conference in Boston, Massachusetts, U.S., August 19, 2025. REUTERS/Brian Snyder/File Photo
FILE PHOTO: United States Department of Justice logo and U.S. flag are seen in this illustration taken April 23, 2025. REUTERS/Dado Ruvic/Illustration/ File Photo

By Nate Raymond

BOSTON (Reuters) -The U.S. Justice Department on Thursday sued the city of Boston and its Democratic Mayor Michelle Wu to challenge an ordinance that restricts police from cooperating with federal immigration enforcement carrying out U.S. President Donald Trump's agenda.

The lawsuit filed in Boston federal court marked the latest in a legal campaign the Republican president's administration has waged over laws adopted by so-called "sanctuary jurisdictions" run by Democrats. The administration contends these laws are impeding Trump's mass deportation agenda.

U.S. Attorney General Pam Bondi in a statement said Boston and Wu "have been among the worst sanctuary offenders in America – they explicitly enforce policies designed to undermine law enforcement and protect illegal aliens from justice."

Wu, who is running for re-election, in a statement called the lawsuit an "unconstitutional attack on our city." She has fiercely supported the city's law, which she said in a letter to Bondi last month ensures Boston remains "a safe and welcoming home for everyone."

The lawsuit targets the Boston Trust Act, a law the city council first adopted in 2014, amended in 2019. It reaffirmed its support for the measure in December as Trump prepared to return to office.

The law bars the Boston Police Department and other city officials from collaborating with federal authorities including at U.S. Immigration and Customs Enforcement to conduct civil immigration enforcement, including by keeping migrants for potential deportation.

The lawsuit argues Boston's law creates obstacles to federal immigration enforcement in violation of the U.S. Constitution's Supremacy Clause, under which federal law preempts state and local laws that conflict with it.

Trump's Justice Department has filed a series of similar cases challenging laws in other states and cities it has labeled "sanctuary jurisdictions" that limit cooperation with federal immigration enforcement, including New York and Los Angeles.

But Wu, in her letter to Bondi last month, said courts have consistently held such laws are "valid exercises of local authority and fully consistent with federal law."

She noted that in July, a federal judge tossed a lawsuit the Justice Department filed against the state of Illinois and the city of Chicago, the first such case the administration filed as part of its campaign.

Wu also noted that Boston's law aligned with a ruling by Massachusetts' highest court in 2017 during Trump's first term that limited how state courts and local law enforcement could assist with federal immigration enforcement.

(Reporting by Nate Raymond in Boston and Kanishka Singh in Washington; Editing by David Gregorio and Stephen Coates)