In early June, the Boulder City Council passed a package of gun control laws in a response to last year’s King Soopers shooting. The measures in Boulder include a new assault weapons ban, which was similar to one the city had tried to pass in 2018, only to have the measure challenged in court under a state pre-emption law that had prohibited cities and counties in Colorado from passing gun laws at the local level.

Governor Jared Polis signed legislation in June 2021 that repealed the pre-emption statute, making Colorado the first state in the nation to take such action and thus allowed Boulder to move forward with six new gun control policies. Denver also took advantage of the pre-emption statute’s termination when it passed a “ghost gun” ban in January, which generally prohibits weapons that can be assembled from kits purchased online.

Although Boulder’s new assault weapons ban has received ample attention, little mention has been made of the Mile High City’s 33-year-old ban. Denver’s ordinance has survived multiple court challenges, including an attempt in 2003 to overturn it using the same pre-emption statute that prevented other local attempts at gun control in Colorado.

On the 10th anniversary of the Aurora theater massacre, in which the shooter used, among other weapons, an AR-15 platform semiautomatic rifle to injure 70 and kill 12 people, we wondered what exactly Denver’s ban says, what prompted it so many decades ago, and if it has had its intended effect.

What Does Denver’s Assault Weapons Ban Prohibit?

Denver’s ordinance makes it unlawful to possess, transfer, or sell an assault weapon within the city and county of Denver. Under this law, an “assault weapon” is defined as:

  • All semi-automatic pistols or centerfire rifles with a detachable magazine with a capacity of more than 15 rounds.
  • All semi-automatic shotguns with a folding stock or a magazine with a capacity of six rounds (or both).
  • Any firearm that’s been modified to operate as a weapon, as defined above.
  • Any part, or combination of parts intended to convert a firearm into an assault weapon, as defined above.

Anyone found in violation of the ordinance can be punished with a fine of up to $999. The assault weapon will also be confiscated and destroyed. However, the ordinance does carve out some exceptions for owners who legally obtained the weapons before the ban went into effect in November 1989 (so long as they had registered the weapons with the city at the time), as well as law enforcement agents, military personnel, and nonresidents who are traveling through Denver without undue delay.

Why Did Denver Pass the Ordinance in 1989?

The final year of the 1980s was a violent one in metro Denver. In March of that year, a man made national headlines when he went on a rampage in Littleton with a MAC-11 submachine gun, killing two women, raping a third, and then wounding three police offers before fatally shooting himself. Meanwhile in Denver, Denver police chief Ari Zavaras claimed his department was dealing with a spike in gang-related shootings. The Denver Post reported the police chief as saying that there was a “terrible” proliferation of assault weapons in the Mile High City—including illegal, fully automatic rifles—being used among the city’s gangs. Zavaras also told a Colfax area neighborhood group, “I certainly am a strong believer in the right to bear arms, but I think we need to take some steps on gun control.” The police chief vowed that he would lobby the city to ban assault weapons. And that he did.

Denver City Council took up the police chief’s recommendation in October 1989 and passed the ban with a 9-4 vote. The measure was controversial right from the start. The Associated Press reported that 700 people packed the Council chambers when the vote passed, with additional picketers protesting outside the City and County Building. The National Rifle Association (NRA) complained the law was too vague in its definition of assault weapons. But City Councilwoman Cathy Reynolds, who died in 2020, was unflinching when she explained her rationale for voting to ban the weapons. “They don’t have any purpose but to blow people away,” she said, “quickly and in large numbers.”

No sooner had Mayor Federico Peña signed the ban into law than critics sought to challenge it in court. Dave Kopel, an attorney who is now the research director of the Libertarian-leaning Independence Institute, helped lead the first challenge to the ordinance in 1990. “I thought it was a plain violation of the Colorado Constitutional right to keep and bear arms,” he says, “and a district court judge agreed with us.”

After an appeal, however, the Colorado Supreme Court ruled 6-1 that Denver did have a compelling interest to keep the ordinance on the books to combat crime. Kopel notes that Denver had to re-write its ordinance because certain parts were deemed imprecise by the district court. Originally, the ordinance spelled out around 40 specific makes and models of what the city considered assault weapons; after the suit, the ordinance was rewritten to focus more on magazine capacity.

The 1990 suit wouldn’t be the last court challenge to Denver’s ban. In 2003, the ordinance came under legal fire once again when Governor Bill Owens signed into law the pre-emption statute that, until 2021, prevented cities from enacting their own gun laws. Denver prevailed once again at the state Supreme Court. Attorneys for the city argued that “home rule”—a provision of Colorado’s Constitution that allows local municipalities to enact legislation covering their jurisdictions without interference by the state government—meant it could continue to enforce its existing 1989 assault weapons ban.

Is Denver’s Assault Weapons Ban Effective?

This is the million-dollar question.

Data provided to 5280 by the Denver Police Department show that, since 2017, police officers have made 18 arrests of individuals for violating Denver’s assault weapons ban. The department says those numbers are not necessarily reflective of every single instance an officer has encountered an individual possessing a firearm in violation of the ban; some arrests could fall under other charges, such as possession of a weapon by a previous offender, aggravated assault, or felony menacing.

The Denver City Attorney’s Office also sent 5280 its most recent data, which show that, since January 1, 2017, the ordinance has been cited in 23 charges brought by the City Attorney’s Office. There were also two charges during 2020 against individuals for possessing outlawed magazines that had capacities of 15 or more rounds.

But has this type of enforcement made Denver an assault-weapons free zone? Not really. Through what some consider a “loophole,” people in Denver can still buy semiautomatic rifles, including weapons commonly considered assault weapons, like AR-15 platform rifles, at area gun stores. In Denver, the City Attorney’s office confirmed, a rifle such as an AR-15 only becomes an “assault weapon” under Denver’s ordinance once it’s combined with a 15-plus round magazine. So long as a Denver resident does not also buy a magazine that fits the gun and holds more than 15 rounds, the purchase is legal.

It’s also worth noting that while Denver has an assault weapons ban, other cities around it do not. The King Soopers shooter, for instance, legally purchased his assault weapon in Arvada. Littleton and Aurora also do not have bans, despite the high-profile mass shootings that have occurred in those cities.

Could Colorado see a more robust, statewide assault weapons ban soon?

Probably not. When asked this question six weeks ago by reporters, Democratic State Senate President Steve Fenberg expressed doubts that a statewide ban is the kind of gun control legislation that would save the most lives, since there are likely tens of thousands of assault weapons in Colorado already, and it’s easy for Coloradans to drive to another nearby state where there are no restrictions.

Still, plenty of Coloradans are still pushing for a statewide ban. Colorado Ceasefire, a nonprofit and a lobbying entity that has successfully advocated for gun control measures in the past—including universal background checks—has also long sought an assault weapon ban. Eileen McCarron, president of Colorado Ceasefire Legislative Action, says she agrees with Fenberg that there are a number of gun control measures besides a statewide ban that the state could pursue to try to reduce gun violence. The state Legislature passed a number of these types of measures in the wake of the King Soopers shooting—like enhancing background checks and establishing an Office of Gun Violence Prevention—that were all seen as less politically controversial than an assault weapons ban. But McCarron also believes an assault weapons ban is an important action for Colorado to take.

“Personally, I would like to see a very tough assault weapons ban,” McCarron says. She adds, of course, that it would be more effective if it were done nationally, along with a mandatory government buyback initiative. “With likely over 20 million assault weapons in our country, it would be an expensive proposition, but it would be incredibly valuable,” she says. “Assault weapons have no business in civilian hands. They are weapons of war, and we need to keep them on the battlefield and out of the hands of civilians, especially troubled young men with grievances.”

Chris Walker
Chris Walker
Chris writes for various sections of 5280 as well as