In 2025, Colorado passed Senate Bill 3, significantly strengthening the state’s existing restrictions on semi-automatic firearmsand large-capacity magazines. For more information see our page on Colorado’s large capacity magazines laws.

Significantly, the bill bans the manufacture of—and significantly restricts the sale of—many semi-automatic weapons. It does not, however, outlaw possession of the banned firearms. Individuals seeking to obtain or transfer certain semi-automatic weapons not deemed prohibited under the bill can do so only after undergoing a background check, receiving approval from their county sheriff, and completing mandatory safety training. The bill also retains exceptions for law enforcement and military personnel, as well as provisions for regulated transfers and storage. The law’s implementation has been delayed until August 2026 to allow time for the development of necessary training programs and systems.¹