DENVER (KDVR) — Gov. Jared Polis signed a measure into law on Thursday requiring people seeking to own a semiautomatic firearm with a detachable magazine to obtain a permit first, and also banning the sale or purchase of rapid-fire conversion devices.

The new law will go into effect on Aug. 1, 2026, requiring citizens to have a permit and safety training to purchase semiautomatic firearms that have detachable magazines.

“High-capacity magazines are what put the ‘mass’ into mass shootings, which is why over a decade ago Colorado Democrats passed legislation to prohibit magazines that hold over 15 rounds of ammunition,” said Sen. Tom Sullivan, a primary sponsor of the bill, in a release. “This legislation is another in the list of policies I have worked on to develop evidence-based solutions and reduce gun violence of all types. The people of Colorado have mandated that we do something about the public health crisis that is gun violence, so that’s what we’re going to do.”

He told FOX31’s Alliyah Sims that this is “just the next step” in addressing gun violence in Colorado, noting that it’s been 664 Fridays since his son Alex was murdered in the Aurora Theatre shooting.

“Certainly every little thing we can do is going to help; there is no magic bill or a wand that you can shake to make everything happen or we would have already done that but every little bit helps,” he said.

Polis said the measure would help push Colorado toward its goal of becoming one of the top 10 safest states. He also advocated for the legislators to look at creating scholarship opportunities for the training, which would be run through Colorado Parks and Wildlife, and permits would be maintained by county sheriff’s offices. He said the current goal is to ensure CPW’s firearm training costs are under $200.

He also advocated for legislators to find a way to ensure prior firearm training and experience, such as peace officer or military training, to allow that training to qualify the citizens for purchase. In a post made later on Thursday, the governor noted that another 14 states require similar permits or safety course completions before purchasing certain firearms.

“Again we want to make sure that it was a real thing to get that learning … overall I really think this bill will make Colorado communities safer and prevent both accidents as well as reducing violence and ultimately that means saving lives while protecting our second amendment rights and of course holding up Colorado’s proud tradition of sport shooting and hunting,” Polis said.

Stella Kaye, the vice president of Students Demand Action, told FOX31’s Alliyah Sims that she believes the bill will make Colorado safer.

“Obviously we know the sole purpose of a high-capacity magazine is to be as deadly and destructive as possible. Obviously by increasing the ammunition that can be fired before someone has to reload,” Kaye said. “In Colorado, we have seen the firsthand effects of the high-capacity magazines. At least 8 of 10 of the deadly shootings involved this style of gun and a high-capacity magazine ban. In Colorado specifically, we had the Aurora shooting, Club Q, King Soopers and the list goes on and on. To say this will make Colorado safer is not an overstatement at all. In fact, I think it’s very true and very clear in the research that has been done about these weapons.”

Gun advocates respond with threats of legal action

Immediately following the signing on Thursday afternoon, the Colorado State Shooting Association, which is the official state association of the National Rifle Association, said it would be filing a lawsuit against the new law.

“This legislation, which imposes unprecedented restrictions on the purchase of semi-automatic firearms through a burdensome permit-to-purchase scheme, represents a direct assault on the Second Amendment rights of law-abiding Coloradans,” CSSA said in a release.

The group has contended that the measure will create a “de facto gun registry” that is maintained by state or local authorities. CSSA also noted that it had presented a petition with over 40,000 signatures urging Polis to veto the bill.

Huey Laugesen, executive director of the CSSA, said that the law is a direct attack on the Second Amendment and does nothing to address crime.

“I don’t see anywhere in this bill where it addresses crime or where it does anything to make Colorado any safer. In fact, I haven’t even heard any arguments from proponents that are substant on why this bill would make Colorado safer,” Laugusen said. “In fact, it only disarms law-abiding citizens and leaves them without the tools they need to defend themselves should they find themselves to be victims of crime. So, it actually, it makes Colorado less safe. It’s just a false statement to say this bill would make anybody any safer.”

CSSA said it would be “actively exploring every legal option” to challenge the law.

The group went one step further, saying it would be working to replace legislators who were in favor of the measure during the 2026 election cycle.

“We will work tirelessly to replace the bill’s supporters with pro-Second Amendment leaders,” said Huey Laugesen, executive director of the CSSA., in a release. “Starting with the most electorally vulnerable legislators, we will ensure that Coloradans’ voices are heard at the ballot box. This fight is far from over.”

The Board of County Commissioners of Rio Blanco County sent a letter to Polis opposing the measure.

“We believe this bill poses significant threats to the economic well-being and cultural identity of our county and other rural communities across Colorado,” the board wrote. “Rio Blanco County is heavily dependent on outdoor activities such as hunting and tourism to sustain its economy. These industries are vital to our revenue streams, job creation, and the overall livelihood of our residents.

“Senate Bill 25-003, in its current form, could severely impact these sectors by introducing regulations that would limit access to outdoor recreation, diminish local tourism, and harm the industries that have long supported our county,” the commissioners wrote to Polis.

They also took issue with a portion of the bill that they said “would criminalize the sale or transfer of specified semiautomatic firearms without state-approved documentation.”

“This provision not only places an undue burden on law-abiding citizens but also imposes significant hardships on small business owners in our community who rely on the lawful sale and transfer of firearms to support their livelihoods,” the board wrote.

El Paso County Sheriff Joseph Roybal responded to the signing of the bill on Friday, calling it “the most atrocious anti-2nd Amendment bill in Colorado history.”

“I am deeply disappointed in the Governor’s decision not to veto Senate Bill 25-003,” said El Paso County Sheriff Joseph. “Public safety experts across the state opposed this legislation, as it will be burdensome on law-abiding citizens, and have no adverse effect on criminals.”

Sheriff Roybal took issue with new hurdles that he said law-abiding citizens must now tackle.

“Small businesses across our state will have to close their doors, and individuals looking to purchase firearms for self-defense will now have to participate in a ‘permit-to-purchase’ system, saddling hard-working Coloradans with unnecessary fees, bureaucratic hurdles, and a state-mandated registration when exercising their constitutional rights,” said Roybal. “Senate Bill 25-003 will do nothing to keep weapons out of the hands of criminals and put small businesses out of business in Colorado.”

Federal politicians advocate for veto of gun bill

Polis said he supports the measure because it will ensure those who buy high-powered firearms have the proper training to safely maintain, store and use them.

“I think, again, that’s a matter of personal responsibility: If you’re going to be purchasing these weapons, it should be your responsibility to make sure you’re safely educated on how to use these weapons,” Polis said during the signing on Thursday. “This legislation builds on our commitment to improve public safety, reduce gun violence, uphold our freedom.”

The CSSA is not the only group vocally against the measure. Republican U.S. Reps. Jeff Crank, Jeff Hurd, Gabe Evans and Lauren Boebert sent a letter to Polis last week, saying that the bill “specifically targets firearms that are commonly owned by Coloradans and allows for arbitrary enforcement against law-abiding individuals.”

They said the measure would be one of the most restrictive gun ownership bills in the U.S., noting that Coloradans who want to purchase a semiautomatic firearm with a detachable magazine must take the training and must obtain an eligibility card from their county sheriff’s office to enroll.

“(A) sheriff has the discretion to deny if they have a ‘reasonable belief’ the individual is ‘danger to themself or others,’” the representatives’ letter said. “Not only does this new scheme come with additional fees and time commitments that no criminal will ever participate in, but it also gives any sheriff hostile to the individual — or semi-automatic firearms in general — carte blanche authority to block the enrollment.”

The measure also prevents sales of gas-operated semiautomatic handguns but does not impact recoil-operated handguns, according to sponsors. The bill also does not impact the possession of currently owned firearms.