Trump went after "sanctuary cities" with an executive order threatening to take away federal funds if they refuse to cooperate with federal immigration authorities in deporting undocumented immigrants. Mayors in cities like Los Angeles, San Francisco, Seattle, Boston and New York, among others, came right back at him, along with some governors. And they may have the constitution on their side.
“Let me be clear,” California's Governor Jerry Brown said. “We will defend everybody—every man, woman and child who has come here for a better life and has contributed to the well-being of our state.”
"Our city is still a sanctuary city and we are going to remain a sanctuary city," said San Francisco Mayor Ed Lee.
“We will not be intimidated by the threat to federal funding,” Boston Mayor Marty Walsh said. “We have each other’s backs. And we have the Constitution of the United States of America on our side. . . . I will use all of my power within lawful means to protect all Boston residents—even if that means using City Hall itself as a last resort.”
Conservatives who yell "States rights!" could have it thrown back in their faces if they try to force cities and states to assist the federal government in rounding up and deporting undocumented immigrants. Apparently, there's something called the Constitution’s anti-commandeering doctrine
A somewhat obscure legal precedent in federal court could help . . . sanctuary cities fight back.
According to the anti-commandeering doctrine, it’s unconstitutional for the federal government to impose “targeted, affirmative, coercive duties” upon state or local government officials. And if Trump follows through on his pledge, sanctuary cities could use it to take on—and perhaps beat—the administration in federal court.
As an attorney in California—one of four sanctuary states—recently pointed out, the doctrine explicitly outlaws the type of retributive threat Trump has floated. Even if the Republican-controlled Congress passed a bill to follow through on the pledge, it could be seen as an infringement on states’ rights.
“The federal government cannot use its taxing and spending powers to coerce states and local governments to enact, administer, or enforce federal law,” Harvard Law School professor Phil Torrey [said].