The U.S. Department of Justice sued Denver on Thursday, Oct. 8, challenging a city ordinance that generally bars law enforcement officers from wearing masks while working within city limits and requires them to display identification visible from at least 25 feet away. The Denver City Council approved the measure unanimously about seven months ago. It applies to federal agents as well as other officers, with exceptions for certain operations, including undercover and SWAT work. Violations can lead to citations or arrest by local police. The Justice Department argues that Denver cannot impose those requirements on federal officers. Its lawsuit invokes the Constitution’s Supremacy Clause, which establishes that federal law takes precedence over conflicting state and local laws. The department also says the rules could expose officers and their families to harassment, doxxing or violence, and interfere with federal operations by limiting officers’ ability to conceal their identities. “The Federal Government gets to decide which equipment federal officers may or may not wear when performing their official duties,” Assistant Attorney General Brett A. Shumate said in a statement. Denver officials say the ordinance responds to residents’ concerns about being approached by masked or unidentified agents during immigration enforcement. Mayor Mike Johnston has argued that people should be able to identify officers who detain them. His office said Denver will defend the law, calling the identification requirement a matter of public safety and transparency. Councilwoman Shontel Lewis, a co-sponsor, previously said some residents were afraid because they could not tell whether people approaching them or asking for information were legitimate officers. The lawsuit names the City and County of Denver, Johnston, City Attorney Michiko Ando Brown and Police Chief Ron Thomas as defendants. The Justice Department says the Denver case is part of a broader effort to challenge local and state policies it views as interfering with federal law enforcement.