The Justice Department filed suit in U.S. District Court for the District of Colorado on May 5 against the City of Denver, challenging the city's 1989 ordinance banning AR-15-style semiautomatic rifles — marking the first time the federal government has taken direct Second Amendment legal action against a local government over a rifle ban of this type. A day later, the DOJ filed a parallel complaint in the same court against the state of Colorado, targeting the statewide prohibition on magazines holding more than 15 rounds, according to The Hill.

The 12-page Denver complaint, signed by Assistant Attorney General Harmeet Dhillon of the Civil Rights Division, applies the Supreme Court's 2022 Bruen standard. AmmoLand reports that the complaint states directly: "When the City banned AR-15 style rifles with standard capacity magazines, it banned an arm in common use for lawful purposes by law-abiding citizens. Therefore, the Ordinance violates the Second Amendment." The suit also names the Denver Police Department as a defendant, alleging that enforcement of the ordinance deprives residents of constitutionally protected rights. Denver's ban has been in effect since 1989 and covers AR-15-style platforms as well as standard-capacity magazines. The DOJ had warned Mayor Mike Johnston on April 28 that the department would sue if the city did not signal willingness to repeal the ordinance by May 5; the city refused.

The separate state complaint challenges C.R.S. §18-12-302, Colorado's magazine-capacity limit. Dhillon wrote that "Colorado's ban on certain magazines is political virtue signaling at the expense of Americans' constitutional right to keep and bear arms," according to Bloomberg Law. Colorado Attorney General Phil Weiser, who is running for governor, called the suit a "dangerous overreach" and vowed to defend the statute. Denver City Attorney Miko Brown dismissed the city-level complaint as "baseless, irresponsible, and a clear overreach of the federal government's power."

Second Amendment organizations welcomed both filings. Bearing Arms reports that NRA-ILA Executive Director John Commerford stated, "The Trump administration has been relentless in defending the Second Amendment, and today's lawsuit against Denver's unconstitutional AR-15 ban is another powerful example." Gun Owners of America called the action "awesome." Acting DOJ Second Amendment Section chief Barry Arrington — a veteran 2A litigator brought into the Civil Rights Division — is leading the litigation effort.

The 10th Circuit Court of Appeals has not issued a definitive post-Bruen ruling on assault weapons bans, making the Denver and Colorado cases potentially pivotal for establishing circuit precedent on semiautomatic rifle and magazine restrictions. The DOJ's press release framed both suits as part of a broader civil rights enforcement push protecting lawful gun owners. No hearing dates have been set in either case; watch for preliminary injunction motions and scheduling orders in the coming weeks as both defendants have signaled they will vigorously contest the complaints.