“These are our neighbors, and we will continue to support our neighbors,” Seattle Mayor Ed Murray told reporters on Wednesday. “We can’t allow ourselves to be divided and sorted out. That’s not America.”

These sentiments were echoed by the mayors of Philadelphia and San Francisco this week. The federal aid that could be cut off if Trump follows through with his plans funds everything from transportation projects to local law enforcement.

Trump and Vitter, along with other opponents of detainer policies, argue that they protect immigrants who have committed violent crimes—the “bad hombres” Trump infamously described during the final presidential debate. Vitter’s law was introduced following the death of Kathryn Steinle, a 32-year-old who was shot by Juan Francisco Lopez-Sanchez, an undocumented immigrant with a nonviolent felony record, in San Francisco last July.

At a campaign rally in August, Trump promised the crowd he would “end the sanctuary cities that have resulted in so many needless deaths,” lamenting the loss of “countless innocent American lives” (though citing just five) and maintaining that “cities that refuse to cooperate with federal authorities will not receive taxpayer dollars.” Numerous studies have shown that both legal and undocumented immigrants are less likely to commit serious, violent crimes than U.S. citizens.

On Thursday in a meeting with Republicans on Capitol Hill, Trump identified immigration as one of his top three priorities. The first item on the 10-point immigration plan posted on his transition team’s website is “Build a wall on the Southern border.”