Can you own a gun and use marijuana in Colorado?
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Under federal law, no — a current marijuana user is prohibited from possessing or purchasing firearms and ammunition, regardless of Colorado's legalization. 18 U.S.C. § 922(g)(3) makes it unlawful for anyone who is "an unlawful user of or addicted to any controlled substance" to possess or receive firearms or ammunition, and marijuana remains a federally controlled substance. Colorado's state-level legalization does not create an exception to this federal rule, and it applies the same to residents and out-of-state cardholders.
The federal prohibition
The question is decided by federal, not state, law. Federal firearms law lists "an unlawful user of or addicted to any controlled substance" among the categories of people who cannot lawfully possess or receive firearms or ammunition.
… who is an unlawful user of or addicted to any controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802)) … to ship or transport in interstate or foreign commerce, or possess in or affecting commerce, any firearm or ammunition; or to receive any firearm or ammunition which has been shipped or transported in interstate or foreign commerce.
Marijuana is a controlled substance under the federal Controlled Substances Act, so a current marijuana user falls within this category. That is true whether the use is recreational or medical, and whether or not the person holds a state medical-marijuana card.
State legality does not change the federal answer
Colorado legalized recreational and medical marijuana at the state level, but a state cannot legalize something for purposes of federal firearms law. Because § 922(g)(3) turns on federal controlled-substance status, Colorado's legalization does not create a firearms exception. The prohibition applies identically to Colorado residents and to visiting cardholders from other states — residency and visitor status are irrelevant to this particular disqualifier.
Buying from a licensed dealer: the certification requirement
The issue also surfaces at the point of purchase. When you buy a firearm from a licensed dealer, federal law requires you to complete a federal firearms transaction form and certify, among other things, that you are not an unlawful user of a controlled substance. Answering that controlled-substance question falsely is itself a separate federal crime, independent of the possession bar in § 922(g)(3).
The exact current wording of the federal form's controlled-substance question is not reproduced here. The form's language has been in flux — a draft revision was under federal review in 2026 following a change in marijuana's federal scheduling, and the final wording was not settled as of July 20, 2026. What has not changed is the underlying rule: a current marijuana user remains a prohibited person under 18 U.S.C. § 922(g)(3) regardless of state legalization or any rescheduling. For questions about your own situation, consult a Colorado attorney.
This is one of several federal and state disqualifiers that determine who may lawfully own a firearm — see what disqualifies you from owning a gun in Colorado and buying a gun in Colorado.
Common questions
Is it legal to own a gun and use marijuana in Colorado?
Not under federal law. 18 U.S.C. § 922(g)(3) prohibits an unlawful user of a controlled substance from possessing firearms or ammunition, and marijuana is federally controlled — so a current user is a prohibited person even though Colorado has legalized marijuana.
Does a medical marijuana card change the answer?
No. The federal prohibition in § 922(g)(3) turns on marijuana's status as a federal controlled substance, not on any state card or program. Holding a state medical-marijuana card does not make firearm possession lawful under federal law.
Can I buy a gun from a dealer if I use marijuana?
Buying from a licensed dealer requires certifying on a federal form that you are not an unlawful user of a controlled substance. A false answer to that question is a separate federal crime, and a current marijuana user is a prohibited person under 18 U.S.C. § 922(g)(3).
Does this apply to out-of-state visitors with a marijuana card?
Yes. The § 922(g)(3) prohibition is federal and applies the same to Colorado residents and out-of-state cardholders alike; residency or visitor status does not matter for this disqualifier.