(Colorado Newsline) Colorado Attorney General Phil Weiser lent his support for a Washington, D.C., law against large-capacity firearm magazines that is facing a legal challenge, as Colorado’s similar law is the subject of a federal lawsuit.

Weiser, a Democrat, joined 18 other attorneys general in filing a court brief last week in support of D.C.’s law, which prohibits magazines with a capacity over 10 rounds of ammunition. The law is being challenged by plaintiffs who argue it violates their Second Amendment rights.

“Each mass shooting is different, but a common denominator in each incident is that the shooter used a large-capacity magazine. As experience has shown, large-capacity magazine limitation laws decrease the deadly impacts of mass shootings by reducing the number of people who will be shot during a mass shooting incident — and save lives. It is critical that courts uphold these common-sense gun safety laws,” Weiser said in a statement.

In the brief, the attorneys general argue that states have a history of limiting forms of ammunition that are not suitable for self-defense, such as large-capacity magazines.

“Like similar laws around the country that impose restrictions on certain types of accessories, ammunition, and weapons themselves, the (large capacity magazine) provision preserves the right of law-abiding, responsible citizens to use firearms for self-defense,” they wrote.

Additionally, they wrote that the law is consistent with historical regulations of “distinctly dangerous” weapons, such as laws banning machine guns or prohibiting a large stockpile of gunpowder.

That historical argument is critical in defending any firearm restriction after the U.S. Supreme Court’s decision last year in New York State Rifle & Pistol Association, Inc. v. Bruen. States must now prove their gun laws have precedent from early in the country’s history, and gun-rights groups have used the Bruen decision to bolster their challenges of firearm regulations. In Colorado, Rocky Mountain Gun Owners have used Bruen to bolster their lawsuits against newly-passed laws on firearm waiting periods and minimum age restrictions.

Weiser joined attorneys general from California, Connecticut, Delaware, Hawai‘i, Illinois, Maine, Massachusetts, Maryland, Michigan, Minnesota, Nevada, New Jersey, New York, Oregon, Rhode Island, Pennsylvania, Vermont and Washington.

RMGO’s legal arm filed a challenge to Colorado’s 2013 high-capacity magazine ban in federal court shortly after the Bruen decision last year. Colorado prohibits magazines that hold more than 15 rounds of ammunition, a law that was enacted in the wake of the 2012 Aurora movie theater mass shooting. The Colorado Supreme Court upheld the law in 2020 when RMGO brought a lawsuit against it in state court.

Most recently in the ongoing federal case, RMGO asked in an Oct. 27 filing for a summary judgment — a decision without going to trial — in favor of a permanent injunction on the law.

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