According to Ava Flanell of Complete Colorado, the new restrictions on buying common firearms fly straight past eye-opening and on to hair-raising:

[With the law in effect], purchasing a semi-automatic rifle, shotgun, or gas-operated handgun would require the following steps:

1. Schedule an appointment with Colorado Parks and Wildlife
2. Undergo a background check by a third party
3. Locate a certified instructor and complete the required training course. A 12-hour class must be taught in two days, not one.
4. Pass a test with a score of at least 90% and be able to demonstrate that you can use the firearm safely. It’s unclear what firearm will be used for this as students cannot purchase a gun before class to bring with them and even if the instructor has a rifle, it most likely won’t be the same as the one they plan to purchase because there are hundreds, if not thousands, of variations.
5. Schedule an appointment with the local sheriff’s office for final approval.
6. Upon receiving approval, when purchasing the firearm, complete another background check and comply with a three-day waiting period.

Each step of this process has fees, amounting to at least $300 total to get an eligibility card that is only valid for five years. If you can’t afford this process, your options of purchasing a semi-automatic rifle, shotgun, or gas operated handgun with a permanently fixed magazine is extremely limited, as no major manufacturer makes such a firearm because it’s too dangerous. 

And, as Stephen Green at Vodkapundit notes, even getting through the process depends on the discretion - and perhaps moods and vicissitudes - of your county sheriff:

Under SB 25-003, it will now take weeks of appointments, classes, and a minimum of $300 — plus your local sheriff's permission, which you may or may not receive, and that he might revoke for a whole host of reasons — to legally purchase the most common firearms in America. I went into the details here earlier this week.

And while the area mainstream media makes it sound fairly mundane...:

BREAKING: Colorado Gov. Jared Polis signs SB25-003 into law, banning the manufacture of and severely restricting the sale of certain semiautomatic firearms with detachable magazines. #coleg #copolitics @DenverChannel pic.twitter.com/kmN56Nt80a

— Brandon Richard (@BrandonLRichard) April 10, 2025

...but via some very convoluted wording, seemingly designed to create criminals, the law essentially bans every semi-automatic, center-fire handgun in Colorado, according to David Kopel and Matt Larosiere:

Senate Bill 3 seems cunningly written. It purports to apply only to the “gas-operated semiautomatic handgun.” (p. 4). The bill then provides five types of gas operation. Cumulatively, the definitions cover almost every centerfire semiautomatic handgun.

I'm not a lawyer, but this law would seem to run smack into the Supreme Court's ruling in the Bruen case that the Second Amendment applies to firearms "in common use" - and it'd take a fine lawyer indeed to claim that center-fire semi-automatic pistols - 85% of the handguns sold today - aren't common.  

The National Shooting Sports Federation agrees:

“This law is unconstitutional on its face. It is a gun control group spurred attack on the Second Amendment rights of those who follow the law,” said Lawrence G. Keane, NSSF’s Senior Vice President and General Counsel. “Colorado lawmakers who claim Gov. Polis’ gun ban will make their state safer have yet to offer legislation that would hold criminals accountable for the criminal misuse of firearms. Instead, they violate the rights of those who obey the law.”

And I can't imagine that the various gun rights groups - the Second Amendment Foundation and the rest - aren't warming up the lawsuit printers even as we speak.