“An ICE detainer is not a warrant; it is not approved by a judge. It does not mean that there has been a finding about the person’s immigration status. It does not even mean that ICE has probable cause to believe the person is deportable. Indeed, ICE makes mistakes—it has regularly issued detainers against citizens or legal residents and denied liberty to people who are not deportable.
“When ICE asks a sheriff to hold a prisoner for up to six extra days, the agency is essentially asking the sheriff to make a new arrest. And Colorado law just does not provide authority to sheriffs to make that arrest. Peace officers in Colorado have authority to deprive persons of liberty when there is probable cause to believe they have committed a crime.
Remaining in the country in violation of federal immigration laws is not a crime. Colorado law does not provide sheriffs any authority to deprive persons of liberty because the federal government suspects they may be subject to civil immigration enforcement proceedings.
The policy goes into effect immediately. From the memo, according to Reuters:
"All persons who are in our custody who currently have a 48-hour ICE hold that is not accompanied by a criminal warrant or some other form that gives … legal authority to hold that person shall be dropped."