Do sanctuary cities violate federal law? Most federal courts that have looked at the question say no. The Constitution bars the federal government from ordering local police and jail staff to carry out federal immigration enforcement, and the one federal statute aimed squarely at sanctuary policies has been found unconstitutional or unenforceable by several courts. The picture is not fully settled — the Trump administration is suing multiple jurisdictions and pushing to cut their funding — but the constitutional framework has consistently protected local governments that decline to participate in federal immigration work.
What Sanctuary Policies Actually Restrict
“Sanctuary city” is a loose label covering very different local rules. Some cities tell their officers not to ask about immigration status during routine encounters. Others prohibit jail staff from honoring Immigration and Customs Enforcement requests to hold someone past a scheduled release. A few limit what local employees can share with federal agents about people in custody.
What these policies do not do is grant legal status, block federal agents from entering the city, or stop ICE from making its own arrests. They govern what local employees do with local resources. That distinction is the whole ballgame in court. The legal question is never whether federal immigration law is valid. It is whether Washington can force local governments to help enforce it.
Why the Tenth Amendment Protects Local Governments
The strongest legal shield for sanctuary policies is the anti-commandeering doctrine. In New York v. United States (1992), the Supreme Court held that Congress cannot order states to administer a federal program. Five years later in Printz v. United States, the Court extended that rule to individual officers, ruling that the federal government cannot conscript state or local law enforcement to carry out federal duties.1Legal Information Institute. Amdt10.4.2 Anti-Commandeering Doctrine The Court’s language was blunt: the federal government “may neither issue directives requiring the States to address particular problems, nor command the States’ officers . . . to administer or enforce a federal regulatory program.”
Sanctuary city litigation almost always turns on this doctrine. When a local government says it will not use its own personnel and budget to enforce federal immigration law, it is exercising the same constitutional prerogative the Supreme Court recognized in Printz. ICE remains free to send its own agents. It just cannot order the city to do the job for it. A March 2026 federal court ruling dismissing the government’s suit against Colorado and Denver said so directly, holding that “the Constitution does not confer upon Congress the power to compel states to implement federal regulatory programs” and that state participation in federal immigration enforcement is “necessarily voluntary.”
Congress does hold sweeping authority over immigration itself. Article VI makes federal law the “supreme Law of the Land,”2Congress.gov. U.S. Constitution Article VI Clause 2 – Supremacy Clause and the Supreme Court has described the federal immigration power as “plenary.”3Congress.gov. ArtI.S8.C18.8.1 Overview of Congress’s Immigration Powers States cannot create their own visa systems or run their own deportation processes. But the same principle that stops states from expanding immigration enforcement also stops the federal government from drafting them into it.
The One Statute That Targets Sanctuary Policies: 8 U.S.C. § 1373
The federal statute most often cited against sanctuary cities is 8 U.S.C. § 1373. It says no state or local government may prohibit its employees from sharing information about a person’s citizenship or immigration status with federal immigration authorities.4Office of the Law Revision Counsel. 8 USC 1373 – Communication Between Government Agencies and the Immigration and Naturalization Service Federal officials have argued for years that sanctuary policies barring local employees from talking to ICE run afoul of this law.
The statute is narrower than it sounds. It covers information-sharing only. It does not require local jails to hold people, grant ICE access to facilities, or physically cooperate with enforcement. Many sanctuary jurisdictions have written their policies to avoid restricting information flow while still declining to actively participate.
Even the narrow information-sharing rule faces serious constitutional problems. In City of Philadelphia v. Sessions, a federal court found that § 1373 violates the Tenth Amendment’s anti-commandeering doctrine because it effectively orders state and local governments not to pass certain kinds of laws. That reasoning tracks the Supreme Court’s decision in Murphy v. NCAA (2018), which struck down the federal ban on state-authorized sports gambling. In July 2025, a federal court dismissing the government’s suit against Illinois, Cook County, and Chicago held that § 1373 “has no preemptive power.” The Second Circuit has taken a more favorable view of the statute, and the Supreme Court has not weighed in, so the question is genuinely unsettled. As of now, the statute has not delivered a clean legal win against sanctuary cities.
ICE Detainers Are Requests, Not Warrants
Much of the public argument focuses on ICE detainers, the forms ICE sends to local jails asking them to hold someone up to 48 hours past their scheduled release. ICE itself has acknowledged that detainers “are only requests” and “don’t impose any obligations on law enforcement agencies.”5U.S. Immigration and Customs Enforcement. Immigration Detainers – Immigration Detainer FAQ They are not judicial warrants. No judge reviews them or finds probable cause before they issue.
That creates a Fourth Amendment problem for jails that comply. Several federal courts have held that holding someone past their release date on an ICE detainer alone, without a warrant or independent probable cause, is an unreasonable seizure. The Ninth Circuit ruled in Gonzalez v. ICE that a neutral decision-maker must review probable cause before someone is detained on an immigration hold. Jurisdictions that honor detainers and get it wrong can face damages. Many local governments adopted sanctuary policies partly to avoid that liability, not just for policy reasons.
Federal Funding as Leverage
When direct legal orders run into anti-commandeering limits, the federal government has turned to money. The main target has been the Edward Byrne Memorial Justice Assistance Grant program, the largest source of federal criminal justice funding for state and local governments.6Bureau of Justice Assistance. Edward Byrne Memorial Justice Assistance Grant (JAG) Program The theory: withhold grants from jurisdictions that will not cooperate with ICE.
Congress can attach conditions to federal spending, but under South Dakota v. Dole, those conditions must be spelled out clearly and must relate to the funding’s purpose.7Justia. South Dakota v. Dole The Byrne JAG statute contains no immigration enforcement conditions. When the Department of Justice tried to add its own — requiring recipients to give ICE jail access, provide advance notice of release dates, and certify compliance with § 1373 — most courts struck them down.
Four of the five federal appellate courts that reached a final decision ruled that the DOJ lacked authority to impose these conditions. The First, Third, Seventh, and Ninth Circuits all held that the executive branch cannot unilaterally add requirements Congress never authorized. Only the Second Circuit upheld the conditions. The reasoning across the majority rulings is straightforward: the power to condition federal spending belongs to Congress, not the Attorney General.
The 287(g) Program Shows Cooperation Is Voluntary
The existence of a voluntary federal partnership program is itself strong evidence that local cooperation is not legally required. Under 8 U.S.C. § 1357(g), the Attorney General can enter into written agreements with state or local agencies allowing their officers to perform certain immigration enforcement functions after federal training and under ICE supervision. The statute expressly says “nothing in this subsection shall be construed to require any State or political subdivision of a State to enter into an agreement.”8Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees
Congress wrote local participation as optional on purpose. If federal law already forced local agencies to enforce immigration rules, a voluntary opt-in program would make no sense. Sanctuary cities are exercising the same choice Congress built into the statute.
Could Sanctuary Officials Be Prosecuted for “Harboring”?
A more aggressive theory that surfaces periodically is that sanctuary policies might violate 8 U.S.C. § 1324, the federal harboring statute. Federal circuits are split on what “harboring” even means. Some apply a broad “substantial facilitation” test. Others require proof that the defendant specifically intended to conceal someone from authorities.
No sanctuary city official has been prosecuted under the statute as of early 2026. Legal scholars at Georgetown Law have noted that declining to share information with ICE or refusing to hold someone without a warrant “should not meet the test for harboring,” though they caution that more aggressive policies could create exposure. A concurring opinion in City of Chicago v. Barr (7th Circuit, 2020) observed that “with the right facts,” a sanctuary policy “could very well facilitate harboring.” That language is dicta, not binding law. The harboring theory remains a political argument, not a proven legal weapon.
What the Laken Riley Act Does and Doesn’t Do
Signed on January 29, 2025, the Laken Riley Act is often described as a crackdown on sanctuary cities. Its actual text points at the federal government, not local jurisdictions. The law requires the Department of Homeland Security to detain noncitizens who are unlawfully present and have been charged with, arrested for, or convicted of burglary, theft, larceny, or shoplifting.9Congress.gov. S.5 – Laken Riley Act 119th Congress (2025-2026) It also lets state governments sue the federal government for injunctive relief when immigration decisions harm the state or its residents by more than $100.
The law imposes no new obligation on local police to cooperate with ICE or to honor detainers. It does not penalize sanctuary jurisdictions. Its practical effect is to give states a legal route to challenge federal enforcement decisions while requiring ICE itself to detain certain people.
Where the Fight Stands Now
The Trump administration has sharply escalated federal action against sanctuary cities since January 2025. An executive order that month directed the Attorney General and the Secretary of Homeland Security to “evaluate and undertake any lawful actions to ensure that so-called ‘sanctuary’ jurisdictions . . . do not receive access to Federal funds.”10The White House. Protecting The American People Against Invasion A follow-up order in April 2025 directed the Attorney General to publish a list of sanctuary jurisdictions and instructed every federal agency to flag grants and contracts to those jurisdictions for “suspension or termination.”11The White House. Protecting American Communities from Criminal Aliens
The Justice Department has filed suits against New York City, Los Angeles, New York State, Colorado, Illinois, and other jurisdictions. Early results largely repeat the earlier pattern. A November 2025 federal ruling permanently enjoined the Department of Transportation from conditioning funding on immigration cooperation. The suit against Illinois, Cook County, and Chicago was dismissed in July 2025. The Colorado and Denver case was dismissed in March 2026. A San Francisco challenge to the administration’s funding threats remains active after a judge denied the government’s motion to dismiss in January 2026.12Portland.gov. Judge Halts Trump Threat to Withhold Dollars from Sanctuary Cities
For now, sanctuary policies as currently structured do not violate federal law under the weight of federal court rulings. Local governments have no constitutional obligation to enforce federal immigration policy. ICE detainers are voluntary. The executive branch cannot rewrite grant conditions Congress never authorized. The one statute aimed at sanctuary policies has been found unconstitutional or unenforceable by multiple courts, and the Supreme Court has not yet weighed in. That could change if Congress passes legislation that explicitly conditions federal funding on immigration cooperation, or if a case reaches the Supreme Court and produces a different answer. Until then, the constitutional architecture continues to favor local governments that choose not to help ICE do its work.