The US Department of Justice sued the state of Illinois, Governor J.B. Pritzker, Chicago Mayor Brandon Johnson, and other state officials Thursday over state laws that limit local law enforcement from aiding federal immigration authorities.

The suit claimed that the state’s Way Forward Act and TRUST Act, Chicago’s Welcoming City Ordinance, and Cook County’s “Policy for Responding to Immigration and Customs Enforcement (ICE) Detainers,” inhibit and obstruct federal agents from enforcing federal immigration laws and regulations:

The challenged provisions of Illinois, Chicago, and Cook County law [make] it more difficult for, and deliberately [impede], federal immigration officers’ ability to carry out their responsibilities in those jurisdictions. These provisions intentionally obstruct the sharing of information envisioned by Congress… thereby impairing federal detention of removable aliens, including dangerous criminals, as required by federal law[.]

The DOJ also argued that the state laws conflict with congressional intent. In particular, the department argued that Title 8 of the US Code, which authorizes immigration agencies to detain individuals on administrative arrest warrants, should supersede Section 15 of the Illinois TRUST Act, which prohibits state law enforcement from detaining individuals on such warrants.

The primary legal justification the DOJ cites against the Illinois laws springs from the Constitution’s Supremacy Clause. The clause grants federal law legal weight over state law when the two conflict over an area in which Congress has authority. The Constitution carves out immigration authority as one of these areas.

“The [federal government] has well-established, preeminent, and preemptive authority to regulate immigration matters,” the suit said.

However, the Supreme Court has held that, while state law does not supplant federal law, the federal government may not force state and local actors to do its bidding. As a result, many cities and states across the US have adopted “sanctuary city” policies similar to Illinois.

Chicago’s ordinance prohibits local law enforcement from accepting administrative warrants. The law also limits local officers from granting “ICE agents access to a person being detained [or] use of agency facilities for… investigative purpose[s].” In addition, the law discourages officers from expending “time responding to ICE inquiries or communicating with ICE regarding a person’s custody status or release date.” However, the ordinance makes an exception for illegal immigrant suspects who have an outstanding criminal warrant or who have been convicted of a felony.

The suit underscores the clash between local and federal powers in the wake of the Trump administration’s controversial immigration policies. For instance, Chicago Mayor Brandon Johnson launched a “Know Your Rights” campaign to educate those who may be targeted by the administration.

In a recent CNN interview addressing the immigration raids taking place across the country, Pritzker emphasized that he fully supports federal policies that specifically target violent or dangerous criminals. However, he also expressed concern over the DOJ targeting law-abiding individuals:

They’re going after people who are law-abiding, who are holding down jobs, who have families here, who may have been here for a decade or two decades. And they’re often our neighbors and our friends… What we need is a path to citizenship for them… We need to protect people… who are doing what we hope that immigrants will do.