U.S. Immigration and Customs Enforcement has issued a subpoena for various law enforcement officials in the city of Denver, Colorado, over their refusal to cooperate with federal authorities with regards to illegal aliens living in the city, the AP reports.

The subpoenas center around four illegal aliens living in Denver who have been arrested for other crimes but are also wanted for deportation. Denver officials have claimed that they are cooperating with federal authorities by already sending information on three of the men, but admitted that they would not send over information on the fourth, who is already in custody, until he is released and thus cannot be as easily tracked down for deportation. Advocates of such policies have claimed that cooperating with ICE would violate the aliens’ civil rights; this is false, since illegal aliens, as non-citizens, do not have any civil rights.

Ryan Luby, a spokesman for Denver’s city attorney, said that they would not cooperate with the new subpoenas because they “were not issued by a court of law and not signed by a judge.” He also falsely claimed that Denver’s sanctuary city policy “fully complies with federal law,” and confirmed that Denver would only “honor the request for the fourth inmate when he is released.”

In response, Henry Lucero, who serves as deputy executive director for ICE’s Enforcement and Removal Operations, said that this explicit refusal to cooperate with federal subpoenas is “a drastic change, and one ICE is forced to do, and puts other agencies on notice that we don’t want this to happen. We want to protect the public.”