How do ICE detainers work and why do some local jails refuse them?

1. What an ICE detainer is and how the process works in practice

An ICE detainer is an administrative request from ICE or a deputized officer asking a jail to either notify ICE before a person’s release or to hold the person for up to an additional 48 hours so federal agents can pick them up and place them into immigration detention ^{[1] [2] [4]}. In practice the detainer usually follows a fingerprint “hit” through programs that share booking data with federal immigration databases, and detainers often flow from that automatic identification process rather than individualized judicial findings ^{[6] [5] [7]}.

2. The legal status: advisory form, not a warrant — and court pushback

Federal courts have repeatedly emphasized that detainers are not judicial arrest warrants and carry no automatic legal authority to prolong state custody; several rulings and settlements have found holding people on detainers without probable cause unconstitutional, and litigation has produced damages and policy changes ^{[3] [8] [2]}. While ICE updated forms to include stronger language about probable cause, scholars note that an ICE administrative determination of civil probable cause does not necessarily authorize local criminal‑justice actors to detain someone beyond their criminal process release authority ^{[8] [9]}.

3. Why many local jails and jurisdictions refuse to comply

Jurisdictions refuse detainers for a mix of legal, fiscal, and policy reasons: courts and legal advisories warn of Fourth Amendment and due‑process liability for holding people on detainers without warrants; localities cite the risk of civil litigation and damages; and many adopt “sanctuary” or non‑cooperation policies to preserve community trust and avoid turning routine policing into immigration enforcement ^{[3] [4] [10] [11]}. States and counties have enacted statutes, policies, or court directives limiting compliance—some prohibit holds without a judicial warrant, others ban compliance altogether—so local practice varies widely ^{[12] [9] [11]}.

4. ICE’s public‑safety argument and federal pressure

ICE frames detainers as a safety and efficiency tool that lets federal agents assume custody in a “safe, controlled environment” instead of making unpredictable community arrests, and the agency warns that noncompliance hampers public safety and interagency cooperation ^{[1] [13]}. The federal government has also used mechanisms such as the “Declined Detainer Outcomes Report” and grant eligibility language to exert political leverage on jurisdictions that decline cooperation ^{[13] [14]}.

5. Tradeoffs, data, and the evolving terrain

Empirical critiques point out that many detainers target people with minimal or no serious criminal history and that ICE has not always acted on detainers—historical ICE data indicated the agency assumed custody in a minority of detainer cases—raising questions about whether jails are holding people unnecessarily ^{[10] [7] [2]}. Recent class‑action settlements and policies aim to inject neutral probable‑cause review and limit unconstitutional detentions, but the landscape remains fragmented: local law, court rulings, state statutes, ICE policy, and political pressure all interact to produce a patchwork of compliance and refusal across the country ^{[2] [12] [9]}.

6. The implicit agendas and how to read competing claims

Advocacy groups (ACLU, ILRC, NILC) emphasize constitutional harms, civil‑liability risk, and community trust to push for noncompliance and policy reform, while ICE and some policy institutes foreground enforcement, public‑safety narratives, and the costs of noncooperation—both sides have institutional incentives: civil‑liberties groups seek to limit federal immigration power; ICE seeks enforcement access and operational ease—so reported claims should be read with attention to those competing agendas and the underlying legal facts ^{[4] [14] [5]}.