Most cities — and critics — have defined “sanctuaries” as places where local police and jail officials don’t always comply with Immigration and Customs Enforcement requests to hold immigrants in jail (after they’d normally be released) so ICE officers can pick them up.
Under federal law, state and local governments can’t prohibit their employees from sharing information with the federal government (if they so choose) about someone’s immigration status.
The Supreme Court doesn’t let the federal government tell cities and states which laws to prosecute, and it can’t force them to help enforce federal law. That’s called “commandeering,” and the Supreme Court has ruled it violates the 10th Amendment. This is why President-elect Trump can’t just decree that all police officers in the US have to assist federal immigration agents whenever possible.
Aurora doesn’t do that. Anyone who is arrested, is fingerprinted and that info is shared (from what I heard) with the FBI and ICE as a matter of routine. If ICE wants the person, they call and say so. The person is then adjudicated, either pays the fine, bond or if jailed is transferred to the appropriate county facility. Of the 10’s of thousands of arrests last year? only 14 did ICE request to pick up.
Hope that clarifies.