What is a sanctuary policy?

Federal law does not define "sanctuary." The Congressional Research Service says there is no legal definition in federal statute for what makes a jurisdiction a sanctuary, and notes that some governments describe themselves that way while others dispute the label. Policies that get the name typically limit how far state or local police, jails and other agencies help federal immigration enforcement, and some limit when a jail will honor a federal detainer request.¹ The CRS notes that traditional policies are often described as falling into three types: "don't enforce" policies that bar local police from assisting federal immigration authorities, "don't ask" policies that bar officials from asking about immigration status, and "don't tell" policies that restrict information sharing.²

Federal definitions vary. A January 2025 executive order described so-called sanctuary jurisdictions as ones that "seek to interfere with the lawful exercise of Federal law enforcement operations,"³ and an April 2025 order defined them as "States and local jurisdictions that obstruct the enforcement of Federal immigration laws."⁴ The Justice Department's list uses criteria such as limits on sharing information about detainees' immigration status and refusing ICE detainer requests "unless there is a warrant signed by a judge."⁵

Governments split over the label. San Francisco calls its 1989 "City and County of Refuge" ordinance its Sanctuary Ordinance and says it promotes public trust and cooperation.⁶ Connecticut Attorney General William Tong said in April 2026 that his state "is not a 'sanctuary' state, whatever that means," calling the term meaningless.⁷ Nevada Gov. Joe Lombardo, announcing an agreement that took Nevada off the Justice Department's list in September 2025, said Nevada "is not a sanctuary state, has never been a sanctuary state."⁸

Many disputes turn on detainers. An immigration detainer is a request ICE lodges after its officers or agents find probable cause that a person is removable. It asks a jail to notify ICE before releasing the person and to hold the person up to 48 hours past the usual release time. ICE itself says "Immigration detainers are only requests,"⁹ and the Congressional Research Service describes them as permissive.¹ Some jurisdictions honor a detainer only when it comes with a warrant signed by a judge, which the Justice Department lists as a sanctuary characteristic.⁵

Courts have raised Fourth Amendment concerns. In 2014 a federal magistrate judge in Oregon ruled for a woman who was kept in a county jail on a detainer after she could have been released, holding that the federal regulation does not require jails to detain people on receiving one and that "the ICE detainer alone did not demonstrate probable cause" to hold her.¹⁰ Texas went the other way: its 2017 law, Senate Bill 4, bans sanctuary city policies and requires local officers to comply with ICE detainer requests, and a federal appeals court upheld nearly all of it against a facial challenge at the preliminary-injunction stage in 2018.¹¹

States and cities rely on the anti-commandeering doctrine. In Printz v. United States in 1997, the Supreme Court held that the federal government may not "command the States' officers, or those of their political subdivisions, to administer or enforce a federal regulatory program."¹² In 2018 it described the doctrine as "the decision to withhold from Congress the power to issue orders directly to the States."¹³

The main federal statute on the other side is 8 U.S.C. 1373, enacted in 1996, which bars state and local governments from restricting their officials from sharing information about a person's "citizenship or immigration status" with federal immigration authorities.¹⁴ A similar provision, 8 U.S.C. 1644, does the same. Courts have disagreed about whether these laws can be squared with the anti-commandeering doctrine, and jurisdictions argue that they cover only immigration status, not information such as release dates.¹

A contrasting approach is a 287(g) agreement, under which local officers are deputized to perform immigration enforcement functions. Federal law says no state or locality is required to sign one,¹⁵ and California's SB 54 bars its police from being deputized for immigration enforcement.¹⁶ A January 2025 executive order directed the Homeland Security secretary to authorize state and local officers to perform immigration functions through such agreements, "with the consent of State or local officials as appropriate."³

The April 2025 order told officials to publish a list of sanctuary jurisdictions and to identify federal funds to them "for suspension or termination."⁴ The Justice Department published its list on August 5, 2025, naming what the Congressional Research Service counted as 13 states, 18 cities and four counties.¹ Nevada was later removed after the state signed an immigration enforcement agreement with the department.⁸

The department also sued states and cities. Dismissing its suit against New York City on October 15, 2026, a federal judge wrote that the case was among nearly a dozen recent challenges of this kind and that the government's challenges had been rejected in all prior ones. The judge found that blocking the city's rules "would result in the commandeering of state and local resources."¹⁷ Another federal judge had dismissed the department's challenge to New York State's limits on courthouse arrests in November 2025, reasoning that "the Tenth Amendment permits a state to decline to assist with federal immigration efforts."¹⁸ The department has appealed some of these rulings, including the dismissal of its suit against Illinois, Cook County and Chicago in October 2025¹⁹ and the New York courthouse ruling in January 2026.²⁰

The two sides disagree about public safety. After an ICE officer shot a man in New York City's Marble Hill neighborhood in October 2026, the Department of Homeland Security said the man had been "released into the community a few days later by reckless Democrat sanctuary policies that put American lives at risk" after a 2023 arrest.²¹ ICE says at-large arrests are "unpredictable and can be dangerous to the public, aliens and federal law enforcement officers."⁹ Jessica Vaughan, director of policy studies at the Center for Immigration Studies, told Congress in 2015 that "Sanctuary policies do nothing to build trust between immigrant communities and local law enforcement."²²

California has argued the opposite. A federal appeals court, declining in 2019 to block SB 54 at an early stage of the federal government's suit, summarized the state's reasoning that "victims and witnesses of crime are less likely to come forward if they fear that an interaction with law enforcement will lead to their removal or the removal of a family member." The court added that it had "no doubt that SB 54 makes the jobs of federal immigration authorities more difficult."²³ San Francisco says its ordinance promotes public trust and cooperation.⁶