How have state and local ‘sanctuary’ policies changed ICE arrest outcomes and detention rates since 2024?
Executive summary
State and local “sanctuary” policies have demonstrably narrowed one of ICE’s traditional pipelines — transfers from local jails via detainers and 287(g)-style cooperation — reducing some jail-origin arrests in jurisdictions that refuse to honor federal requests (Prison Policy [1]; ILRC p1_s9). At the same time, federal enforcement has shifted tactics and expanded capacity since late 2024, producing higher overall detention numbers even as local noncooperation blunts certain ICE arrest outcomes (ICE dashboards [2]; American Immigration Council [1]1).
1. How sanctuary rules changed the jail-to-ICE pipeline
Hundreds of counties and cities curtailed compliance with ICE detainer requests and 287(g)-type deputizations following court rulings and advocacy campaigns, which directly reduced the pool of people handed over from local custody to ICE in those places (ILRC [3]; Prison Policy p1_s1). Reports show that local jails historically comprised a large share of ICE arrests — as much as 45% since January of the Trump administration referenced — meaning noncompliance can materially shrink ICE’s yield from routine bookings (Prison Policy [1]5). That shift is exactly the policy lever sanctuary jurisdictions targeted: limit transfers, keep people in community-oriented supervision, and deny the federal agency easy access to detained populations (American Immigration Council [1]3).
2. Federal countermeasures and changing arrest practices
The federal government responded by changing tactics: increasing targeted enforcement operations, large-scale workplace raids, “roving” arrests, and relying more on transfers from Customs and Border Protection and U.S. Marshals contracts to place people into ICE custody (American Immigration Council [4]; Prison Policy p1_s1). ICE’s own dashboards covering arrests and detentions through December 31, 2024 document expanded activity and new reporting on trends, which suggests that gains from local noncooperation have been at least partially offset by federal resource increases (ICE dashboards p1_s5). ICE public releases also show discrete operations in sanctuary jurisdictions — for example a January 2025 sweep in New York that resulted in 54 arrests — showing that sanctuary status does not immunize communities from federal enforcement (ICE press release p1_s3).
3. Who is being detained: shifting profiles and contested figures
Analyses and journalism since late 2024 indicate a shift in the profile of those detained: a rising share of people booked into ICE custody have no criminal convictions, according to data cited by outlets and researchers, a fact that sanctuary advocates highlight to show the social cost of cooperation (CalMatters citing Cato data p1_s4). Scholarly and NGO reporting raises concerns that enforcement targets are being broadened beyond traditional public-safety priorities, a trend that increases detention overall even if local jails send fewer people directly to ICE (Brennan Center; American Immigration Council [5]; [1]1).
4. Data gaps, limits, and why outcomes look mixed
Any firm causal claim about sanctuary policies reducing national detention rates is constrained by incomplete public data: ICE releases do not capture every pathway into custody (for example federal criminal prosecutions, some U.S. Marshals placements, or Border Patrol arrests) and state-level arrest-rate calculations depend on methodological choices and population estimates (Prison Policy [1]; ICE detention file p1_s2). Multiple independent trackers and FOIA-derived databases provide slices of the picture, but they also show that while local noncooperation reduces certain types of transfers, federal agencies have filled gaps with alternative enforcement levers (Deportation Data Project [6]; Prison Policy [1]5).
5. Net effect since 2024: sanctuary policies blunt but do not stop detention expansion
Taken together, the evidence supports a mixed but decisive conclusion: sanctuary policies have meaningfully changed ICE arrest outcomes at the local level by reducing transfers from cooperating jails and limiting some information-sharing (ILRC [3]; Prison Policy [1]5), yet they have not prevented a dramatic increase in detention driven by federal enforcement priorities and new operational approaches since late 2024, as ICE and independent analyses document rising bookings and expanding detention usage (ICE dashboards [2]; American Immigration Council [1]1). The policy implication is clear in the reporting: local resistance alters the pathway and lowers certain arrest rates locally, but without federal policy change or reductions in detention capacity, overall detention rates can rise regardless.