When Immigration and Customs Enforcement announced its new training program for local law enforcement on Monday, the agency billed the program as a way for police in so-called “sanctuary” cities and states to cooperate with ICE.

Does ICE’s new program really allow police to skirt around their state and city’s sanctuary policies? According to legal experts, probably not.

Though sanctuary policies vary greatly, most people agree that, for such a policy to have teeth, it must limit ICE’s ability to issue “detainer requests.” An ICE detainer request works like this: When local law enforcement officers arrest somebody, they take that person’s fingerprints and send the information to the federal government. If ICE determines that the person is in the country illegally, the agency might issue a detainer request asking local police to keep the person in jail. Even if a judge has ordered someone’s release, or if police realize they arrested the wrong person, an ICE detainer request asks the police to hold that person in jail for up to 48 hours longer, in order to give ICE agents time to come re-arrest them….

Pacific Standard Magazine