The U.S. Justice Department sued Denver in federal court Oct. 8, seeking to overturn city rules that bar law enforcement officers—including federal immigration agents—from covering their faces or concealing their identities during certain encounters with the public. The ordinance, approved by the Denver City Council in March 2026, applies when officers interrogate, detain or arrest someone in the city, including inside city-owned buildings. It also bars civil immigration enforcement on city-owned or city-operated property, potentially including parks and the National Western Complex. City documents say violations can carry up to 300 days in jail and a $999 fine. The federal complaint names Denver, Mayor Michael Johnston, City Attorney Michiko Ando Brown and Police Chief Ronald Thomas as defendants. The department argues the ordinance unconstitutionally interferes with federal law enforcement and is asking the court to declare it invalid and permanently prevent the city from enforcing it. No court ruling was reported with the filing. Johnston has said Denver will fight the lawsuit. He argues that officers should be identifiable and accountable, saying residents need to know whether someone approaching them is a law enforcement officer. He has described masked officers without identification as a public-safety concern. Associate Attorney General Stanley E. Woodward Jr. argued that local governments lack authority under the Constitution’s Supremacy Clause to regulate the federal government. He also said the ordinance could put federal officers at risk and disrupt federal operations. Denver officials and supporters have framed the rules as a response to residents’ concerns about transparency and safety during immigration enforcement. Councilmember Flor Alvidrez previously called the measure a limited effort to give people a greater sense of security, rather than a comprehensive immigrant-rights policy. The ordinance also raised concerns about how it would be enforced. Brian Pacelko, president of the Denver Police Protective Association, warned at a council committee meeting that local officers could face difficult confrontations with federal agents if they were required to enforce the rules. The case adds Denver to a broader national dispute over local policies governing federal immigration enforcement. The Justice Department says it has brought similar challenges in several states and cities, including Maryland, New York, Virginia, Connecticut, New Jersey, California, Philadelphia and Milwaukee.