The U.S. Department of Justice sued Denver on Thursday, Oct. 8, challenging a city ordinance that restricts law enforcement officers, including federal agents, from concealing their faces during arrests and detentions. The lawsuit names Denver, Mayor Mike Johnston, City Attorney Miko Brown and Police Chief Ron Thomas. The department argues that the ordinance violates the Constitution’s Supremacy Clause, which limits local governments’ ability to regulate federal operations. It is seeking a permanent court order preventing Denver from applying the restrictions to federal officers. Denver’s City Council unanimously approved the ordinance in March. It also requires officers to display identification, with exceptions for undercover work and certain safety situations. The Justice Department’s complaint says violations could carry penalties of up to 300 days in jail and a $999 fine. Federal attorneys argue the rules could expose officers to harassment and retaliation. The lawsuit points to court rulings blocking similar restrictions in California, New York, Virginia and Philadelphia. The city has defended the ordinance as a measure to make law enforcement more accountable. “Denverites deserve to know who is arresting them and what they’re being arrested for,” Johnston spokesperson Jon Ewing said in a statement. The case adds to a series of disputes between Denver and the Trump administration over immigration enforcement. The Justice Department sued Denver and Colorado last year over policies limiting cooperation with ICE. In February, Johnston largely barred ICE agents from city property, and in September Denver sued to keep ICE away from polling places. A federal judge will now decide whether Denver can set rules for how federal officers identify themselves and whether they may cover their faces while carrying out enforcement actions.