The U.S. Department of Justice filed federal lawsuits against both the City of Denver and the State of Colorado on consecutive days this week, making good on threats delivered nine days earlier. Both suits land in U.S. District Court for the District of Colorado and rest on the same constitutional argument: Colorado has been violating the Second Amendment, and the federal government is done waiting.
The Denver suit, filed Tuesday, May 5, targets the city’s 1989 ordinance banning semi-automatic rifles, including AR-15-style firearms. The state suit, filed Wednesday, May 6, challenges Colorado Revised Statute §18-12-302 — the 2013 magazine ban enacted a year after the Aurora theater mass shooting — which makes it a crime to sell, transfer, or possess any magazine capable of accepting more than 15 rounds. The Colorado Department of Public Safety, which enforces the ban through the Colorado State Patrol and Colorado Bureau of Investigation, is named as co-defendant in the state suit. Both complaints were signed by Barry K. Arrington, acting chief of the DOJ’s Civil Rights Division Second Amendment Section.
The Second Amendment states that “the right of the people to keep and bear Arms, shall not be infringed.” The Fourteenth Amendment makes that right binding on every state — no state law, and no state court ruling, overrides it. The U.S. Supreme Court confirmed the individual right to keep and bear arms in District of Columbia v. Heller (2008), extended it fully to states and cities in McDonald v. City of Chicago (2010), and in New York State Rifle & Pistol Association v. Bruen (2022) established the controlling test: any gun restriction must be rooted in the historical tradition of firearm regulation at the time of the founding. Modern public safety rationales are no longer legally sufficient. Arms in common use by law-abiding Americans are protected.
Acting Attorney General Todd Blanche announced the Denver filing with a statement on justice.gov: “The Constitution is not a suggestion and the Second Amendment is not a second-class right. Denver’s ban on commonly owned semi-automatic rifles directly violates the right to bear arms.” Assistant Attorney General Harmeet Dhillon, whose Civil Rights Division brought both suits, said the DOJ would “defend law-abiding Americans from restrictions such as those we are challenging in these cases.” On the state suit, Dhillon was direct: Colorado’s magazine ban is “political virtue signaling at the expense of Americans’ constitutional right to keep and bear arms.”
The state complaint names specific firearms the magazine ban affects beyond rifles. The Glock 17 — identified in the complaint as one of the most popular handguns sold in the United States — and the SIG Sauer P365, also a top seller, are both sold standard with magazines Colorado bans. The DOJ’s complaint states that Colorado itself has previously admitted the magazines it bans are in common use by law-abiding Americans — a concession that cuts against the state’s own legal defense under Bruen. The Denver complaint notes that as of 2021, Americans owned at least 28 million modern sporting rifles, with roughly 2.8 million AR-style semi-automatic rifles sold in 2020 alone — about 20 percent of all firearms sold that year.
Colorado Attorney General Phil Weiser called the state suit a “dangerous overreach” that “turns the mission of the DOJ’s Civil Rights Division on its head” and pledged to “vigorously defend our state large-capacity magazine limit law.” Weiser is also the Democratic candidate for governor, running on gun control as a campaign plank while defending these same laws in court. Denver Mayor Mike Johnston answered the April 28 pre-suit letter on the steps of the City and County Building: “Our first job is to keep Denverites safe, and we will not be intimidated out of doing it.” Denver City Attorney Miko Brown called the DOJ’s demand “baseless, irresponsible, and a clear overreach of the federal government’s power.” Both Weiser and Brown have pointed to prior court rulings upholding the restrictions — but those rulings came under standards Bruen has since displaced. The Colorado Supreme Court upheld the magazine law unanimously in Rocky Mountain Gun Owners v. Polis (2020) on state constitutional grounds.
Huey Laugesen of the Colorado State Shooting Association said his organization had spent more than a year advocating for the DOJ to act. “It definitely puts these elected officials on notice, who have thought for a long time that they can just get away with passing legislation that blatantly violates the Second Amendment to the United States Constitution,” Laugesen said. The man who signed both federal complaints has his own Colorado history with these statutes. Arrington previously represented Rocky Mountain Gun Owners in a state-level challenge to Colorado’s magazine ban, then dismissed that case with prejudice in 2024, unable to carry the burden of proof under Bruen at the time. He now leads the federal effort against the same law from inside the DOJ, with the full resources of the Civil Rights Division behind him.
The Colorado lawsuits are part of a broader DOJ enforcement campaign. The department also sued Washington, D.C., over its semi-automatic firearms ban in the same period and filed 34 ATF rulemaking notices the week of April 29 rolling back gun regulations nationally — the Denver and Colorado suits are the fourth and fifth civil rights actions the DOJ has filed in defense of Second Amendment rights since January 2025. The Tenth Circuit Court of Appeals handed Colorado a separate Bruen setback ten days before the suits landed, rejecting the state’s legal framework in a ghost gun serialization case and ordering a new constitutional test — the Tenth Circuit ordered the lower court to apply the Bruen historical tradition test to Colorado’s ghost gun serialization requirement.
The 2026 legislative session, which adjourns May 13, has continued adding to Colorado’s gun law stack. Senate Bill 26-043, tightening firearm barrel transfer requirements, passed the House 33-32 last week. House Bill 26-1144, banning 3D-printed firearms, awaits Governor Polis’s signature. Senate Bill 25-003 — a permit-to-purchase requirement for semi-automatic rifles — takes effect August 1, 2026. No court dates have been set in either the Denver or Colorado cases as of May 8.
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