To clarify further: cannabis legalization and decriminalization varies a lot by jurisdiction, but has rapidly accelerated in recent years. Even “legalized” and “decriminalized” varies significantly. Some states and jurisdictions permit commercial sales and others permit only cultivation, possession and gift exchange. Washington is fairly odd in that it allows commercial sale but doesn’t allow cultivation without a (medical or industrial) license. North Carolina is odd in that it’s decriminalized but has no medical. It’s effectively a grey market in all states with commercial, because you can’t legally use any form of electronic payment (despite many industry efforts to circumvent the restriction).

This all routes back to the Cole memo issued by the Obama DOJ, which (correctly IMO) identified federal jurisdiction as limited to interstate commerce, and effectively issued guidance to states that the federal government won’t intervene if it determines that local governments are making a good faith effort to prevent product or sales from crossing state lines.

Full legalization is almost definitely inevitable, but these sorts of patchwork laws will persist until federal law changes. Increasingly it seems likely that several holdout states will remain so until that time and may remain so even after the fact.