Sanctuary cities are constitutional under current Supreme Court precedent. The Tenth Amendment’s anti-commandeering doctrine bars the federal government from forcing state and local governments to carry out federal programs, and courts have applied that rule repeatedly to block attempts to conscript local police into immigration enforcement or strip funding from cities that decline to cooperate. The picture is not perfectly settled: one federal statute on information-sharing remains contested, state governments can impose their own anti-sanctuary mandates on their cities, and the current federal administration is pushing an aggressive litigation campaign that may test the framework in new ways. But the core constitutional principle protecting sanctuary policies rests on three decades of Supreme Court decisions and is unlikely to collapse.
What the Anti-Commandeering Doctrine Says
The Tenth Amendment reserves to the states any powers the Constitution does not grant to the federal government. From that foundation, the Supreme Court has built a clear rule over three cases: Congress cannot order state or local governments to administer federal regulatory programs.
In New York v. United States (1992), the Court struck down a federal law that gave states a supposed “choice” between regulating radioactive waste under federal instructions or taking ownership of it. Congress, the Court held, “may not commandeer the States’ legislative processes by directly compelling them to enact and enforce a federal regulatory program.”1Justia. New York v. United States, 505 U.S. 144 (1992) The federal government can offer incentives, regulate private conduct directly, or preempt conflicting state laws. It cannot draft state legislatures into service.
Printz v. United States (1997) extended that protection to state and local executive officers. The Brady Act had temporarily required local law enforcement to run background checks on handgun buyers. The Court struck the requirement down, with Justice Scalia writing that federal power “would be augmented immeasurably and impermissibly if it were able to impress into its service—and at no cost to itself—the police officers of the 50 States.”2Justia. Printz v. United States, 521 U.S. 898 (1997) The task was minor, temporary, and arguably useful. The Court still said no. If the federal government cannot require a sheriff to run a five-minute background check, it almost certainly cannot require a city to spend jail space, staff time, and budget dollars enforcing immigration law.
Murphy v. NCAA (2018) closed a loophole. A federal law had prohibited states from authorizing sports betting, and the Court struck it down. “The distinction between compelling a State to enact legislation and prohibiting a State from enacting new laws is an empty one,” the Court wrote.3Supreme Court of the United States. Murphy v. National Collegiate Athletic Association, 584 U.S. 453 (2018) That matters for sanctuary cities. Congress cannot ban cities from adopting noncooperation policies any more than it can order them to cooperate.
Why the Supremacy Clause Does Not Override This
Critics of sanctuary policies often invoke the Supremacy Clause, which makes federal law “the supreme Law of the Land.” The intuition is that immigration is federal law, federal law overrides local policy, so cities must comply. That reasoning confuses two very different powers. The Supremacy Clause lets the federal government invalidate state laws that conflict with federal statutes. It does not let the federal government commandeer local employees to carry out federal duties.
Sanctuary cities do not create their own immigration rules or grant anyone legal status. They decline to volunteer their resources for federal enforcement. A city that refuses to hold someone in jail on an immigration detainer is not obstructing federal law; it is choosing not to do the federal government’s job for free. Federal agents remain free to make arrests, issue warrants, and deport people using federal resources.
The Supreme Court drew this distinction in Arizona v. United States (2012), which struck down most of Arizona’s attempt to build a state-level immigration enforcement scheme. The Court held that Congress occupies the field of immigration so thoroughly that “even complementary state regulation is impermissible” in areas like alien registration.4Justia. Arizona v. United States, 567 U.S. 387 (2012) That cuts both ways. If immigration enforcement belongs solely to the federal government, the federal government must bear the cost of its own enforcement rather than shifting it onto local budgets.
The One Genuinely Unsettled Piece: 8 U.S.C. § 1373
One federal statute sits at the center of nearly every sanctuary city lawsuit. Section 1373 of Title 8 says that no state or local government “may prohibit, or in any way restrict” its employees from sharing immigration-status information with federal immigration authorities.5Office of the Law Revision Counsel. 8 USC 1373 – Communication Between Government Agencies and the Immigration and Naturalization Service The federal government treats this as a baseline compliance requirement and argues that any sanctuary policy restricting information flow violates it.
Its constitutional status is genuinely unresolved. In 2018, two federal district courts ruled that § 1373 violates the anti-commandeering doctrine because it prevents cities from controlling how their own employees communicate, effectively displacing local authority over local personnel. Those decisions were affirmed on appeal, though the appellate courts resolved the cases on other grounds and sidestepped the constitutional question.6Congressional Research Service. Sanctuary Jurisdictions – Legal Overview
After Murphy, the argument that § 1373 is unconstitutional gained ground. The Court’s holding that Congress cannot prohibit states from changing their own laws maps onto a statute that prohibits cities from restricting their employees’ communications. Telling a city “you cannot instruct your police officers to stop sharing immigration data” looks a lot like the negative command the Court rejected in Murphy. No circuit court has squarely applied that logic to § 1373 in a published opinion, so the question is still open.
What Happens When Congress Tries to Use Money as Leverage
Unable to directly order cities to cooperate, the federal government has repeatedly tried to attach immigration-cooperation conditions to federal grants. This runs into its own constitutional walls.
South Dakota v. Dole (1987) laid out the ground rules for conditional federal spending. Conditions must serve the general welfare, must be stated unambiguously, must relate to the purpose of the federal program, and must not violate other constitutional provisions.7Justia. South Dakota v. Dole, 483 U.S. 203 (1987) The relatedness requirement is where most sanctuary-funding fights end up. If a grant funds body cameras or drug treatment, tacking on an immigration-cooperation requirement has no logical connection to the program’s purpose.
NFIB v. Sebelius (2012) added a further limit. There, the threatened loss of all existing Medicaid funding for states that refused to expand the program amounted to what the Court called “a gun to the head,” constituting “economic dragooning that leaves the States with no real option but to acquiesce.”8Justia. National Federation of Independent Business v. Sebelius, 567 U.S. 519 (2012) Coercion at that scale is unconstitutional even when smaller strings would be allowed.
The main funding battleground has been the Edward Byrne Memorial Justice Assistance Grant program.9Bureau of Justice Assistance. Edward Byrne Memorial Justice Assistance Grant (JAG) Program FAQs In 2017, the Department of Justice announced that Byrne JAG recipients would need to give federal immigration authorities access to local jails and 48 hours’ notice before releasing anyone wanted for removal. The Seventh Circuit struck those conditions down in City of Chicago v. Sessions, holding that the Attorney General had no statutory authority to impose them. “The power of the purse rests with Congress,” the court emphasized, and Congress had never authorized immigration-enforcement conditions on Byrne JAG funds.10Justia Law. City of Chicago v. Sessions, No. 17-2991 (7th Cir. 2018) The executive branch cannot invent new conditions for existing grants.
More recent proposals would extend immigration-compliance conditions beyond law enforcement grants, including to Community Development Block Grant funds that support housing and infrastructure.11The White House. Protecting American Communities from Criminal Aliens That would make the relatedness requirement from Dole even harder to satisfy.
Fourth Amendment Liability When Cities Honor Detainers
Constitutional analysis also runs in the other direction. When cities do cooperate with certain federal requests, they can create legal liability for themselves. When ICE issues an immigration detainer, it is asking a local jail to hold someone for up to 48 hours past the point when that person would otherwise be released. ICE itself acknowledges that detainers “are only requests” and “don’t impose any obligations on law enforcement agencies.”12U.S. Immigration and Customs Enforcement. Immigration Detainers
A detainer is not a judicial warrant. Holding someone in jail without a warrant, probable cause, or a pending criminal charge raises serious Fourth Amendment problems. Multiple federal courts have found that local agencies can face civil liability for detaining people solely on ICE requests. The Third Circuit ruled in Galarza v. Szalczyk that because detainers are voluntary, local agencies “may be held liable for their role in causing an unlawful detention” when no valid legal basis for the hold exists. Cities that comply with every detainer are volunteering to absorb the legal risk that the federal government created. Several jurisdictions have paid substantial settlements after holding U.S. citizens or legal residents on detainers that turned out to be wrong.
When Cooperation Is Voluntary: The 287(g) Program
Federal law does provide a path for local agencies that want to participate in immigration enforcement, and it is entirely voluntary. Section 287(g) of the Immigration and Nationality Act authorizes ICE to enter into formal agreements with local law enforcement agencies, granting designated officers limited immigration authority under ICE’s supervision.13U.S. Immigration and Customs Enforcement. Delegation of Immigration Authority Section 287(g) Participating officers receive federally funded training and operate under one of several models, including screening people booked into local jails for immigration violations.
The existence of this program reinforces the constitutional case for sanctuary cities. Congress designed 287(g) as a voluntary framework precisely because it understood that local immigration enforcement cannot be mandated. If the federal government already had the power to compel local cooperation, there would be no need for a program built around signed agreements and federal training.
The Boundary: State Anti-Sanctuary Laws
The constitutional analysis changes when the pressure comes from a state government rather than the federal government. The anti-commandeering doctrine protects states from federal overreach, but cities are legally considered subdivisions of their state. They have no equivalent Tenth Amendment shield against state directives.
A growing number of states have passed laws prohibiting their cities and counties from adopting sanctuary policies. These laws typically require local law enforcement to cooperate with ICE detainers, share immigration-status information, and allow federal officers access to local jails. Penalties can include loss of state grant funding, daily fines reaching $25,000, removal of local officials from office, and in some states, criminal charges against officials who refuse to cooperate.
Courts have generally upheld these state-level mandates. Because cities derive their authority from the state, a state can direct how its political subdivisions interact with federal agencies in ways that the federal government cannot. A city in a state with an anti-sanctuary law faces a genuine legal bind: federal courts say the city cannot be forced to cooperate by the federal government, but state law may require cooperation as a condition of the city’s own authority. That conflict has not been cleanly resolved.
The Current Litigation Push
The current federal government has escalated the fight against sanctuary jurisdictions to a degree not seen before. In April 2025, the President signed an executive order directing the Attorney General and the Secretary of Homeland Security to publish a list of sanctuary jurisdictions, notify them of “potential violations of Federal criminal law,” and identify federal funds eligible for suspension or termination.11The White House. Protecting American Communities from Criminal Aliens The order also directed the pursuit of “all necessary legal remedies” against jurisdictions that remained in defiance after notification.
The Department of Justice published a formal list of sanctuary jurisdictions in August 2025 and filed lawsuits against major cities and states, including New York City, Los Angeles, Boston, Chicago, and the states of California, New York, and Illinois.14U.S. Department of Justice. Justice Department Publishes List of Sanctuary Jurisdictions Several of those cases remain in active litigation as of early 2026. Some jurisdictions, like Louisville, revoked their sanctuary policies after receiving threatening letters from the DOJ rather than face a lawsuit. Sanctuary jurisdictions have filed their own suits challenging federal enforcement actions, and federal courts have issued injunctions blocking some of the administration’s funding threats.
The underlying constitutional principles have not changed. The weight of Supreme Court precedent still favors the constitutionality of sanctuary policies, and cities that decline to use their own resources for federal immigration enforcement are exercising a right the Court has recognized repeatedly over three decades. How the current wave of cases resolves at the circuit and Supreme Court level over the next few years will determine whether that framework holds firm or whether the federal government finds new tools to pressure local compliance.