US Immigration and Customs Enforcement (ICE) detainers—the requests from ICE to a state or local law enforcement agency to hold someone until the person can be taken into immigration custody—have been instrumental in supporting the growing number of deportations from the United States. However, as migrant detentions expanded after 9/11, law enforcement agencies have been increasingly reluctant to comply with ICE's detainers, due to the cost incurred by detention centers when holding immigrants for an extended period and the possible violation of migrants’ civil rights. Such reluctance has earned these law enforcement agencies the label of “sanctuary cities.” ICE has denounced this behavior, arguing that it interferes with the agency's ability to obtain custody of convicted criminals and makes communities less safe. Using data on detainers at the local law enforcement-agency level, we assess ICE's claims. We find that sanctuary policies do not hinder ICE's ability to obtain custody of convicted criminals and question the argument that such policies might make communities less safe. These findings are relevant for migration scholars and policymakers interested in gaining a better understanding of the public-safety implications of sanctuary policies aimed at immigrants in various receiving nations, including Canada, the UK, and the United States.

美国移民和海关执法局 (ICE) 的拘留者——ICE 向州或地方执法机构提出的在该人被移民拘留之前拘留某人的要求——在支持越来越多的美国驱逐出境方面发挥了重要作用。然而，随着 9/11 之后移民拘留的扩大，执法机构越来越不愿意遵守 ICE 的拘留者的规定，因为拘留中心长时间拘留移民会产生成本，并且可能侵犯移民的公民权利。这种不情愿为这些执法机构赢得了“庇护城市”的标签。ICE 谴责了这种行为，认为它干扰了该机构获得已定罪罪犯的监护权，并使社区不那么安全。我们使用当地执法机构级别的拘留者数据来评估 ICE 的索赔。我们发现庇护政策不会妨碍 ICE 获得对已定罪罪犯的监护权，并质疑此类政策可能使社区不安全的论点。这些发现与移民学者和政策制定者相关，他们有兴趣更好地了解针对加拿大、英国和美国等不同接收国移民的庇护政策对公共安全的影响。