The Trump administration stepped up its legal fight over the president’s crackdown on undocumented immigrants by suing Illinois and Chicago, claiming their “sanctuary” policies prevent local officials from cooperating with federal immigration enforcement.

The lawsuit accuses city, county, and state authorities of ‘minimally enforcing—and oftentimes affirmatively thwarting’ federal immigration law.

The Trump administration is suing Chicago over what are known as sanctuary laws. The administration claims the nation’s third-largest city “thwarts” federal efforts to enforce immigration laws.