YSK that if you obtain a state marijuana card, whether for medical or recreational use, you can no longer legally purchase firearms.

As many of you are aware, at least 29 states have laws on the books saying that some form of marijuana is legal for sale or consumption. Many of these states also issue cards to purchase marijuana. If you obtain one of these cards, you are giving up your ability to purchase guns as marijuana is still a schedule 1 drug on the federal level.

Buying a firearm is a federal process conducted by gun dealers with a Federal Firearms License, and those FFLs have to conduct a background check via the ATF Form 4473 (PDF). Recently, question 11e was updated to say thus:

Are you an unlawful user of, or addicted to, marijuana or any depressant, stimulant, narcotic drug, or any other controlled substance? Warning: The use or possession of marijuana remains unlawful under Federal law regardless of whether it has been legalized or decriminalized for medicinal or recreational purposes in the state where you reside.

Lying on this form is a crime punishable with up to 5 years in prison. A 9th Circuit Appeals Court case in 2016 determined that even just having the card is enough to assume that you are a (federally) unlawful user.

The question of whether you can still possess firearms you already had before you obtained the card is currently up in the air. Recently Gov. Tom Wolf of Pennsylvania stated there would be no confiscations of firearms from marijuana card holders, but about a month ago law enforcement in Honolulu, Hawaii were debating confiscating weapons from the 30 or so individuals that were both registered marijuana users and registered gun owners. If you are a card holder or plan on getting one, please realize that at this time you are potentially opting out of your 2nd Amendment rights, and consider that if this is something that matters to you in any way.