A Colorado law passed in 2025 established new requirements for individuals planning to purchase semiautomatic weapons.

Here’s what residents should know before Senate Bill 003 goes into effect on Aug. 1.

From a ban to a training course

For decades, advocates have been pushing for a ban on semiautomatic weapons with detachable magazines, which they have described as “assault weapons,” though efforts escalated following the Columbine High School shooting in 1999.

After the 2012 movie theater shooting in Aurora, the Colorado legislature passed House Bill 1224, which prohibited the sale, transfer and possession of ammunition magazines capable of holding more than 15 rounds. However, some advocates wanted more, arguing that shootings with such high casualty rates are only possible because of semiautomatic weapons with detachable magazines, which fire off rounds at high speeds and take less time to reload.

A decade later, lawmakers introduced House Bill 23-1230, which proposed prohibiting the sale, manufacturing and purchasing of semiautomatic weapons with detachable magazines. The measure, sponsored by former Rep. Elisabeth Epps, D-Denver, and former Sen. Rhonda Fields, D-Aurora, failed to pass through its first committee. However, the following year, Epps teamed up with former Rep. Tim Hernandez, D-Denver, and Sen. Julie Gonzales, D-Denver, to introduce a similar measure in House Bill 1292. The bill proved more successful that time, passing through the House before failing in Senate committee in the final weeks of the 2024 session.

Things took a turn during the 2025 legislative session, however. While Epps and Hernandez were no longer part of the Colorado General Assembly, Gonzales and Sen. Tom Sullivan, D-Centennial introduced a third attempt at a ban with Senate Bill 003.

As introduced, the bill was very similar to its predecessors. However, sponsors faced a significant roadblock, as Gov. Jared Polis said he would not sign the ban into law. In an effort to get the governor on board, sponsors amended the bill to allow individuals to purchase semiautomatic firearms with detachable magazines, but only if they complete a required firearm safety course administered by Colorado Parks and Wildlife.

The bill passed through both chambers, with all Republicans and a handful of Democrats voting in opposition. The governor signed the bill into law on April 10, 2025.

How it works

According to Colorado Parks and Wildlife (CPW), eligible Coloradans interested in purchasing a semiautomatic firearm with a detachable magazine must go through a multistep process.

First, they must fill out an application on the state’s Firearms Safety System, which will go live on July 20, though some counties will not be reviewing applications until Aug. 1. Once the application is submitted, it will go to the applicant’s local county sheriff. In order for the application to be processed, applicants must provide a name-based background check and photo ID to their sheriff’s office and pay a $52 fee to CPW, with a possible additional fee from the sheriff’s office.

The sheriff’s office will then review each application. If an individual is determined eligible to purchase a semiautomatic firearm, they will be issued an eligibility card, which is good for five years. Eligibility card information will be entered into the Firearms Safety System database.

Once applicants receive an eligibility card, they will need to enroll in a safety course with a verified firearms instructor. The instructor will determine whether an applicant has to take the basic or extended version of the safety course, depending on whether the person has already taken a hunter education course.

CPW said the courses will teach students about safe handling of firearms and ammunition magazines, child safety and safe storage, firearm deaths associated with mental illness, extreme risk protection orders and victim awareness.

After finishing the course, applicants will need to pass an exam and a hands-on practical with a score of 90% or higher. Once they pass, applicants are eligible to purchase semiautomatic firearms with detachable magazines until their eligibility card expires, after which they will need to go through the process again.

The debate

Senate Bill 003 racked up dozens of hours of debate between lawmakers and advocates on both sides. It is the subject of at least one lawsuit challenging its constitutionality.

For supporters, who see Senate Bill 003 as the logical next step after the magazine capacity limit, the law marks a crucial step toward reducing gun violence.

“These weapons that (SB 003) is mainly focused on are powerful weapons that have been used in very, very awful situations,” said Eileen McCarron, the legislative director for Colorado Ceasefire. “If you look at mass shootings, almost all of them have been using assault weapons of some sort.”

The perpetrators of some of Colorado’s deadliest mass shootings, including Columbine, Aurora, Club Q in Colorado Springs, and King Soopers in Boulder, used semiautomatic weapons to carry out their attacks, she said.

“They’re very, very dangerous weapons,” said McCarron. “These weapons have things that make them far more dangerous than just a regular hunting rifle.”

During floor debate on the bill last year, sponsor Speaker Pro Tempore Andrew Boesenecker, D-Fort Collins, noted that firearms are the No. 1 cause of death for American children.

“As a former public school teacher who is the parent of three children in our public schools, there is not a day that goes by, not a single day, that I don’t worry,” he said. “And I know I’m not alone in that.”

Boesenecker said similar measures in other states have been tried in courts and proven constitutional multiple times, even after the landmark 2022 Bruen case. 

Opponents of Senate Bill 003 are skeptical of the law’s constitutionality.

Mark Oliva of the National Shooting Sports Foundation, a trade organization that represents the firearms industry, noted a recent case in which a judge issued an injunction on the implementation of Virginia’s semiautomatic firearms ban, which was set to go into effect on July 1.

“There is nowhere in the founding of our nation that there were any laws that required you to obtain permission to exercise your Second Amendment rights,” Oliva said. “We condemned the law when Governor Polis signed it. We said it was an unconstitutional move to infringe upon the Second Amendment rights of lawful citizens.”

Firearms manufacturers and sellers have also expressed worries about the impact Senate Bill 003 and other laws like it would have on businesses, as the top-selling rifle in the country, the AR-15, is a semiautomatic weapon with a detachable magazine.

Others have argued that, despite the staccato of laws passed over the years restricting access to firearms, shootings — mass or individual — have not stopped.

While Oliva agreed that something needs to be done to stop gun violence, he argued that bills like Senate Bill 003 go after law-abiding citizens, rather than criminals.

“What they’re doing is creating an obstacle for people to be able to lawfully possess and purchase the most common rifle in America today that is used for all legal purposes,” said Oliva.

“I will challenge Governor Polis or Senator Sullivan or anybody else that had their fingerprints on crafting this law to show me anywhere in SB 3 where they’re holding a criminal accountable for breaking the laws,” he said. “What they’re doing is creating more laws that make it more difficult for those who obey the law to actually exercise their Second Amendment rights.”