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.

The Trump administration sued officials in Illinois, Chicago and Cook County on Thursday over policies that limit cooperation with federal immigration enforcement authorities, accusing them of obstructing its immigration crackdown.

The lawsuit argues that the U.S. Constitution’s Supremacy Clause “prohibits Illinois, Chicago, Cook County, and their officials from obstructing the Federal Government’s ability to enforce laws that Congress has enacted or to take actions entrusted to it by the Constitution.”