BOSTON — A federal judge in Rhode Island ruled this week that it’s unconstitutional to require states to cooperate on immigration enforcement actions to get funding through the Federal Emergency Management Agency for disasters.

A coalition of 20 state Democratic attorneys general, including Maine’s Aaron Frey, filed a federal lawsuit in May claiming that the Trump administration is threatening to withhold billions of dollars of disaster-relief funds unless states agree to certain immigration enforcement actions.

In a ruling granting a summary judgment to the plaintiffs and denying one for the federal government, U.S. District Judge William Smith found that the “contested conditions are arbitrary and capricious” and that the actions are unconstitutional because they are “coercive, ambiguous, unrelated to the purpose of the federal grants.”

“Plaintiff States stand to suffer irreparable harm; the effect of the loss of emergency and disaster funds cannot be recovered later, and the downstream effect on disaster response and public safety are real and not compensable,” Smith wrote.

Frey, in a written statement Thursday, lauded the decision.

“The federal government continues to use threats of withholding grants — this time ones slated for disaster relief and anti-terrorism efforts — to meet its arbitrary and inhumane immigration goals,” he wrote. “Importantly, the court found that there was no reasonable or lawful justification for this other than to compel the states’ compliance. My colleagues and I will continue to hold the President and his Administration to account under the law and the Constitution.”

Rhode Island Attorney General Peter Neronha, who initiated the suit, said the ruling was a “win for the rule of law and reaffirms that the President may not pick and choose which laws he and his Administration obey.”

In their complaint, states argued that for decades they counted on federal funding to prepare for, respond to and recover from disasters. But they argued conditions put forward by the Trump administration requiring them to commit state resources to immigration enforcement put at risk funding for everything from mitigating earthquake and flood risks to managing active wildfires.

The Department of Homeland Security “seek to upend this emergency management system, holding critical emergency preparedness and response funding hostage unless States promise to devote their scarce criminal enforcement resources, and other state agency resources, to the federal government’s own task of civil immigration enforcement beyond what state law allows,” the plaintiffs wrote.

They argued successfully that this not only was unconstitutional but that it violated the Administrative Procedure Act, a law that governs the process by which federal agencies develop and issue regulations.

“The conditions are arbitrary and capricious under the APA because DHS failed to provide a reasoned explanation, failed to consider the reliance interests of the states, and departed from longstanding funding practices without adequate justification,” Smith wrote.

The government had argued that the challenge was moot since it had already decided to exclude 12 of the 18 programs from having to comply with the immigration requirements. For the remaining programs, the government argued that this was a contract dispute that should be resolved in the Court of Federal Claims.

“Even if that were not so, Congress intended for the FEMA grant programs at issue to address national security and terrorism concerns that rely on the cooperation that the conditions promote,” the government wrote in court documents. “Congress did not preclude the placement of the challenged conditions on the grant programs at issue, and Plaintiffs have not established a likelihood of success on the merits with respect to these programs.”

A spokeswoman for DHS, Tricia McLaughlin, said in a statement Wednesday that the administration believes that “cities and states who break the law and prevent us from arresting criminal illegal aliens should not receive federal funding.”

“The Trump Administration is committed to restoring the rule of law. No lawsuit, not this one or any other, is going to stop us from doing that,” she said.