How do ICE detainers work and what are the constitutional limits on local compliance?
Executive summary
ICE detainers are administrative requests—typically the I-247 form—asking state or local jails to hold an individual for up to 48 hours beyond the time they would otherwise be released so ICE can transfer custody [1]. Compliance by local agencies is voluntary in federal law and constrained by constitutional (Fourth and Tenth Amendment) and state-law limits; courts and settlements in recent years have curtailed routine honoring of detainers without judicial process [2] [1] [3].
1. What an ICE detainer actually is—and is not
An ICE detainer is a non‑binding request from Immigration and Customs Enforcement asking a jail to maintain custody for a short window so ICE can assume custody, not an arrest warrant or judicial order authorizing a new seizure [1] [3]. ICE historically used detainers to instigate transfers that account for a large share of interior ICE arrests, but the form itself does not, on its face, provide state officers independent statutory or constitutional authority to continue a detention [4] [1].
2. Constitutional guardrails: the Fourth Amendment on detention
Prolonging a person’s custody solely on the basis of an ICE detainer has been repeatedly challenged as a warrantless seizure that can violate the Fourth Amendment’s probable‑cause and seizure limits; federal courts have held that detainers without judicial process can create unlawful arrests and render local agencies liable [1] [5]. Recent litigation and settlements have imposed procedural requirements on ICE’s detainer practice—most notably limiting the use of certain ICE detainer forms or requiring neutral review—because the existing practice failed to provide protections comparable to those required by the Fourth Amendment [3] [6].
3. Constitutional guardrails: the Tenth Amendment and anti‑commandeering
The federal government cannot constitutionally compel states or localities to enforce federal immigration policy; the anti‑commandeering doctrine rooted in the Tenth Amendment prohibits directives that force state officers to administer federal programs, and courts have reaffirmed that the federal government may not commandeer state or local law enforcement into immigration enforcement [2] [7]. That constitutional principle underpins the legal permissibility of “sanctuary” policies that limit or condition cooperation with ICE, and explains why neither the Constitution nor federal statute requires localities to honor detainer requests [2] [8].
4. State law, local policies, and liability risks
State statutes and court rulings shape how local agencies can respond: several state courts have found that honoring detainers can constitute a new arrest under state law and exceed local arresting authority, and some states have enacted laws or directives limiting cooperation with ICE [9] [10]. Local agencies face legal exposure—under the Fourth Amendment and state tort or statutory claims—if they detain people beyond lawful release times on the basis of a detainer, which is why hundreds of counties and cities have adopted restrictive policies or stopped compliance after litigation and advocacy [5] [8] [11].
5. Federal pressure and limits on federal leverage
The federal government has used tools—threats to condition funding, “name and shame” lists, and 287(g) agreements—to press local compliance, but those tactics bump against constitutional and statutory limits: spending‑clause constraints, anti‑commandeering doctrine, and judicial rulings restrict the federal ability to force local enforcement of immigration law [12] [9]. ICE has also changed operational practices—such as using Requests for Notification rather than detainers in certain contexts and negotiating settlement terms to address procedural defects—but courts emphasize that administrative adjustments do not eliminate local liability where constitutional rights are implicated [3] [1].
6. Bottom line: discretionary request vs. legal risk
Practically, a detainer remains an ICE request that localities may accept, condition, or reject, but accepting it without judicially sufficient probable cause can create constitutional liability and run afoul of state law; conversely, state and local limits on cooperation are constitutionally protected choices, not nullifications of federal power [13] [11] [5]. Where ambiguity remains—about when a detainer is supported by an ICE warrant, when state law permits a civil arrest, or how new federal practices interact with court mandates—litigation, state directives, and negotiated settlements continue to shape the operational boundary between ICE’s administrative reach and constitutional limits [7] [3] [14].