On the campaign trail President Trump promised to cancel all federal funding to sanctuary cities who do not cooperate with the federal government in enforcing federal immigration law. True to his word, President Trump has signed an executive order stating that sanctuary cities are “not eligible to receive Federal grants,” with some unclear exceptions.   

Whether and when this executive order will lead to cities losing federal funding, and how much, is unknown. New York City mayor Bill de Blasio has vowed to sue the federal government “the minute action to withhold funding” occurs.

Much has been written about what legal theories could be relied on to challenge the cancelling of federal funds. It is difficult to gauge the strength of these theories because all are rooted in Supreme Court precedent applying broad constitutional provisions in fact contexts different than this executive order.

Below are a few possible legal theories cities may rely on if they sue the federal government. The first three are based on limitation the Supreme Court has found in the Constitution’s Spending Clause. In short, the Spending Clause allows the federal government to place conditions on money states and local government receive—to a point. The final theory rests on the Tenth Amendment.     

If sanctuary cities sue the federal government they are likely to allege that cancelling all federal funding is “coercive” under the Spending Clause. In NFIB v. Sibelius (2012), Chief Justice Roberts famously described the federal government’s plan to withhold all Medicaid funding if states refused to agree to the Obamacare Medicaid expansion as a coercive “gun to the head.” In that case states stood to lose over 10 percent of their overall budget by not agreeing to the Medicaid expansion. Many sanctuary cities would stand to lose that percent of their budget—and more—if they lost all federal dollars.   

As George Mason University School of Law professor Illya Somin points out in a Washington Post article, the fact that the statutory language of most, if not all, federal grant programs to cities doesn’t require cities to assist the federal government with immigration enforcement is another possible ground for sanctuary cities to challenge this executive order. In decisions, including Pennhurst State School and Hospital v. Halderman (1981), the Supreme Court has stated that when Congress, using its spending power, imposes conditions on the receipt of federal funds it must do so “unambiguously.”

The Supreme Court also has held that per the Spending Clause conditions Congress place on grants must be “germane” or “related to” the federal interest in the grant program. In South Dakota v. Dole (1987), the Court noted approvingly that South Dakota didn’t challenge the “germaneness” of the Secretary of Transportation withholding a percent of highway funds to states which did not raise the drinking age to 21.

Now imagine if Congress “unambiguously” conditioned a number of federal grant programs for roads, health care, education, etc. on cities assisting with federal immigration enforcement. Cities could argue these conditions are not “germane” or “related to” the federal interests in funding roads, health care, or education.

The Tenth Amendment reserves powers not delegated to the federal government to the states. The Supreme Court has interpreted the Tenth Amendment to contain an anti-commandeering requirement where states and local governments cannot be required “to enact or administer a federal regulatory program.” For example, in Printz v. United States (1997), the Court struck down a federal law requiring local police departments to perform handgun background checks until the federal government could manage the task. Sanctuary cities could argue that they cannot be commandeered into enforcing federal immigration law.