Is it illegal to be a sanctuary city
Executive summary
Being a “sanctuary city” is not per se a federal crime—there is no single federal statute that outlaws a local government declaring sanctuary practices—but sanctuary policies occupy a contested legal and political gray zone where federal preemption, funding conditions, lawsuits, and state bans collide, producing patchwork outcomes across courts and legislatures [1]. Recent federal actions—lists, litigation, and proposed laws to restrict funding—show the federal government can try to punish or compel compliance, yet constitutional limits and differing judicial rulings mean the answer depends on which legal tool is used and where .
1. What “sanctuary city” actually means — vague label, local detail
“Sanctuary city” is not a legal term with a single definition; it generally describes jurisdictions that limit local cooperation with federal immigration enforcement—practices that vary widely and can be formal ordinances, policies, or informal practices such as declining to ask about immigration status or refusing ICE detainer requests [1]. Because the label covers a spectrum—from refusal to hold detainees on ICE requests to broader “don’t ask” policies—legal exposure and federal responses turn on the specific policy language and conduct, not the headline of being a sanctuary [2].
2. Federal power and the limits: preemption and anti‑commandeering
Congress has plenary immigration authority under the Supremacy Clause, and federal statutes contemplate cooperation mechanisms like detainers, but constitutional doctrines—especially anti‑commandeering—constrain the federal government’s ability to force states or cities to perform federal tasks, so a blanket federal decree that sanctuary cities are illegal faces constitutional contours and contested judicial review . Legal scholars and courts have concluded that while federal law preempts conflicting state laws, the federal government cannot commandeer local police to enforce federal immigration law, which is why disputes often end up litigated over the nuance of specific requirements .
3. Tools the federal government uses — lists, lawsuits, and funding threats
Recent administrations have used publicity and administrative tools—publishing lists of sanctuary jurisdictions and bringing enforcement lawsuits—to pressure localities, and Congress has repeatedly proposed statutes to bar funds to sanctuary jurisdictions or to condition grants on cooperation, illustrating a multi‑pronged federal strategy that mixes political pressure with legal claims . These measures can have real effects: DOJ has published lists and filed suits to compel compliance , and bills in the 119th Congress seek to withhold federal grants from jurisdictions designated as sanctuaries .
4. State-level counters: bans, penalties, and the patchwork of authority
Some states have passed laws banning sanctuary policies or requiring cooperation with ICE—creating a second layer of legality where a locality could be penalized under state law even if not criminally liable under federal statutes—so it is entirely possible to be legally barred from maintaining sanctuary policies within certain states [3]. Conversely, in states without such laws, localities have more latitude to adopt sanctuary practices, subject to federal challenges and potential funding conditions .
5. Courts, precedents, and the unsettled landscape
Federal courts have split on the reach of federal authority to coerce or punish sanctuary jurisdictions; past litigation (e.g., suits raised in the mid‑2010s and ongoing cases cited by CRS and DOJ materials) shows mixed outcomes and many disputes turn on statutory interpretation, standing, and specific policy text rather than a universal rule that sanctuary policies are illegal . The absence of a single definitive Supreme Court pronouncement and continuing congressional proposals means the legal status remains case‑specific and evolving .
6. Bottom line and limits of available reporting
There is no across‑the‑board federal criminal prohibition on a city declaring sanctuary status; however, sanctuary policies can be lawfully constrained by state bans, challenged in federal court, or targeted by funding conditions and enforcement actions—outcomes that vary by jurisdiction and the legal mechanism employed [1]. Reporting and primary sources describe these mechanisms and disputes, but definitive claims about future litigation outcomes or the constitutionality of specific contemporary funding actions are beyond what these sources can conclusively resolve today .