The U.S. Department of Justice filed a lawsuit Wednesday against the state of Colorado, challenging a 2013 law that bans possession of so-called large-capacity magazines holding more than 15 rounds. The complaint, lodged in the U.S. District Court for the District of Colorado, argues that the statute unconstitutionally infringes on the Second Amendment rights of law-abiding citizens to keep and bear arms in common use for lawful purposes.

Colorado Revised Statutes § 18-12-302 prohibits the sale, transfer, or possession of large-capacity magazines except for those owned before July 1, 2013, and maintained continuously by the owner. The law targets magazines that come standard with popular semi-automatic firearms, including AR-15-style rifles, which the Department of Justice describes as the most popular rifles in America. Law-abiding Americans own hundreds of millions of such magazines for self-defense, hunting, sport shooting, and other lawful activities.

"Colorado’s ban on certain magazines is political virtue signaling at the expense of Americans’ constitutional right to keep and bear arms," said Assistant Attorney General Harmeet K. Dhillon of the Justice Department’s Civil Rights Division. "Under my direction, the Division’s Second Amendment Section will continue to defend law-abiding Americans’ rights against unconstitutional restrictions on their right to possess arms, which are owned by tens of millions of their fellow citizens."

The lawsuit invokes the Supreme Court's 2008 decision in District of Columbia v. Heller, which held that the Second Amendment protects arms in common use for lawful purposes. It follows a similar suit filed Tuesday against the city of Denver over its longstanding ban on assault weapons and magazines exceeding 15 rounds.

Colorado enacted the magazine ban in 2013 in response to the 2012 Aurora theater shooting, where the gunman used a large-capacity magazine to fire more than 60 rounds rapidly, killing 12 people and injuring dozens. The state Supreme Court upheld the law in 2020 under the state constitution, but did not address federal Second Amendment claims.

Colorado Attorney General Phil Weiser responded swiftly to the federal action. "Using federal civil rights law to put Coloradans at greater risk of gun violence is a dangerous overreach by the Justice Department, and this lawsuit turns the mission of the DOJ’s Civil Rights Division on its head," Weiser said. "Large-capacity magazine laws are responsible policies that satisfy Second Amendment protections, decrease the deadly impacts of mass shootings, and save lives."

The suit comes amid heightened scrutiny of gun restrictions following the Supreme Court's 2022 decision in New York State Rifle & Pistol Association v. Bruen, which requires firearm regulations to align with historical traditions. Prior challenges to Colorado's magazine ban have had mixed results, including a 2024 federal dismissal of a related case.

The Justice Department seeks a declaratory judgment that the law is unconstitutional and an injunction barring enforcement. Colorado officials have indicated they will vigorously defend the statute.