"All 64 Colorado counties observe a policy of not holding illegal immigrants without an arrest warrant signed by a judge."  Is it legal to hold someone suspected of committing any crime without a warrant?  The problem is that only ICE can enforce federal immigration laws, but does not have have the personnel to apprehend suspected illegal aliens without local agencies' having to "hold" them indefinitely.  On the other hand, some will consider the entire state to be a "sanctuary" state.