Under federal law, you cannot legally buy a gun with a medical marijuana card. Cannabis is still a Schedule I controlled substance federally, and the Gun Control Act bars any “unlawful user of or addicted to any controlled substance” from buying or possessing firearms — a rule the ATF applies to medical cardholders even in states where the program is fully legal. That answer is under real pressure in 2026: the ATF has narrowed who counts as an “unlawful user,” several federal appeals courts have struck the ban down as applied to cannabis, and the Supreme Court is expected to rule on the question by summer. Today, though, the prohibition still stands.
Why the Card Blocks the Sale
The Gun Control Act makes it illegal for any unlawful user of a controlled substance to ship, transport, receive, or possess a firearm or ammunition, and it bars dealers from selling to anyone they have reason to believe uses one.1Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts Because marijuana sits on Schedule I alongside heroin and LSD, the federal government treats any cannabis use as unlawful, no matter what your state’s medical program says.2Office of the Law Revision Counsel. 21 USC 812 – Schedules of Controlled Substances
The ATF spelled this out in a 2011 open letter to every federally licensed dealer in the country. The letter told dealers that “any person who uses or is addicted to marijuana, regardless of whether his or her State has passed legislation authorizing marijuana use for medicinal purposes, is an unlawful user of or addicted to a controlled substance, and is prohibited by Federal law from possessing firearms or ammunition.”3Bureau of Alcohol, Tobacco, Firearms and Explosives. Open Letter to All Federal Firearms Licensees It also told dealers that simply knowing a customer holds a state medical marijuana card gives them “reasonable cause to believe” the person is a user, which means the sale cannot go through.
What Happens at the Gun Counter
Every purchase from a licensed dealer requires ATF Form 4473, the Firearms Transaction Record. After the August 2023 revision, Question 21.f asks whether you are “an unlawful user of, or addicted to, marijuana or any depressant, stimulant, narcotic drug, or any other controlled substance.” The form carries a bold warning that marijuana use and possession remain unlawful federally “regardless of whether it has been legalized or decriminalized for medicinal or recreational purposes in the state where you reside.”4Bureau of Alcohol, Tobacco, Firearms and Explosives. Firearms Transaction Record – ATF Form 4473
Answer “yes” and the dealer cannot sell you the gun. Answer “no” while knowing you’re a current user, and you’ve made a false statement on a federal form. That is a separate crime carrying up to five years in prison.5Office of the Law Revision Counsel. 18 USC 924 – Penalties There is no honest path through the form that ends with the sale approved.
After you submit the form, the dealer runs your information through the FBI’s National Instant Criminal Background Check System. NICS looks at criminal records and other disqualifying factors, but it is not built to detect cannabis use or to cross-reference state medical marijuana registries, and most states do not share those registries with federal law enforcement.6Federal Bureau of Investigation. Firearms Checks (NICS) That does not make the transaction legal. The risk is not being flagged at the counter; the risk is that possessing a firearm as a cannabis user is a federal felony no matter how the gun was acquired.
What If You Already Own Guns
The prohibition is not only about buying. It covers possession. If you already own firearms and then obtain a medical marijuana card and begin using cannabis, continuing to keep those guns puts you in violation of the same statute.1Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts Courts have read the interstate-commerce hook in the law broadly enough to cover essentially any firearm.
Private sales don’t cure the problem either. Some buyers assume that skipping Form 4473 through a private transaction sidesteps the issue. It doesn’t. The possession ban applies whether you bought the gun from a dealer, from a friend, or inherited it. Enforcement against individual gun-owning cardholders has been rare in practice, with charges usually surfacing in the course of other investigations, but rarely enforced is not the same as legal.
The Two Penalties You’re Exposed To
- False statement on Form 4473. Lying about drug use on the transaction form is a federal offense punishable by up to five years in prison, a fine, or both.5Office of the Law Revision Counsel. 18 USC 924 – Penalties
- Possessing a firearm as an unlawful user. A separate provision covers the possession itself. The Bipartisan Safer Communities Act of 2022 raised the maximum penalty for this offense to 15 years in prison.7Congress.gov. S.2938 – Bipartisan Safer Communities Act
Either conviction is a felony, which permanently strips your firearm rights going forward. Defense costs, fines, and employment fallout compound the damage.
What’s Changing in 2026
The ATF’s Narrower Definition of “Unlawful User”
In January 2026, the ATF issued an interim final rule that tightens who counts as an “unlawful user of or addicted to any controlled substance.” Under the older framework, a single use within the past year could be enough. The new definition requires evidence that a person “regularly uses a controlled substance over an extended period of time continuing into the present.”8Federal Register. Revising Definition of Unlawful User of or Addicted to Controlled Substance
The rule explicitly says “a person is not an unlawful user of a controlled substance if the person has ceased regularly unlawfully using the substance, or if the person’s unlawful use is isolated or sporadic.”8Federal Register. Revising Definition of Unlawful User of or Addicted to Controlled Substance For a cardholder who uses cannabis regularly, the ban still applies. Someone whose use is occasional, or who has stopped, has a real argument they no longer fit the definition. The comment period on the interim rule runs through June 30, 2026.
The Supreme Court Case
The Supreme Court granted review in United States v. Hemani and heard oral arguments on March 2, 2026.9Justia U.S. Supreme Court Center. United States v Hemani The case squarely presents whether the federal government can categorically bar cannabis users from possessing firearms, and it should resolve a split among the federal appeals courts. The Fifth Circuit held in United States v. Daniels (January 2025) that disarming someone “solely for their prior, occasional, or habitual marihuana use” is unconstitutional, finding that the statute “imposes a far greater burden on Second Amendment rights than our history and tradition of firearms regulation can support.”10United States Court of Appeals for the Fifth Circuit. United States of America v Patrick Darnell Daniels, Jr. Other circuits have upheld the ban, some categorically and some only after individualized proof of dangerousness. Your practical risk today depends on which circuit you live in, and a decision in Hemani is expected by summer 2026. During argument, Justice Gorsuch called it “an odd case” for the government to defend the ban while simultaneously pursuing rescheduling.
Rescheduling — and Why It Doesn’t Automatically Fix This
The Department of Justice published a proposed rule in May 2024 to move marijuana from Schedule I to Schedule III, following recommendations from HHS and the FDA. The rule drew nearly 43,000 public comments and is still awaiting a required administrative hearing. A December 2025 executive order directed the Attorney General to complete rescheduling “in the most expeditious manner.”11The White House. Increasing Medical Marijuana and Cannabidiol Research
Rescheduling to Schedule III would not, on its own, restore gun rights for medical cannabis users. The firearms ban covers unlawful users of any controlled substance, and Schedule III drugs are still controlled substances. What could change is the word “unlawful”: a patient using cannabis under a valid state prescription might no longer count as an unlawful user if marijuana were treated as a drug with accepted medical use. That question will need to be worked out by courts or Congress. Until then, the prohibition holds.
The Bottom Line for Cardholders Today
As of mid-2026, federal law still says no. A medical marijuana cardholder who uses cannabis regularly is a prohibited person under federal firearms law. Answering Question 21.f honestly on Form 4473 will block the sale, and answering dishonestly is its own felony. The ATF’s revised definition of “unlawful user” gives some room to occasional or former users, and the Supreme Court could reshape the entire question within months. Anyone weighing a purchase or worried about firearms they already own should talk to a firearms attorney in their state, because the law you’re operating under this summer may not be the law you’re operating under this fall.