The Trump administration is suing Chicago over what are known as sanctuary laws. CHICAGO — The Trump administration sued Chicago on Thursday alleging that 'sanctuary' laws in the nation's third-largest city “thwart" federal efforts to enforce immigration laws.

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 comes as Chicago mayor Brandon Johnson is expected to testify before the House Oversight Committee next month.