This is exactly it, and everyone crowing about "credit card companies shouldn't be able to restrict what you can buy" didn't read the article. Mastercard doesn't want to restrict people from buying things they are legally allowed to buy, because more Mastercard transactions = more money for them. But they have to follow the laws, and being complicit in illegal purchases puts them at risk for litigation.

No point in getting mad at Mastercard for this. Get angry at our politicians who still haven't legalized marijuana. If marijuana is legalized federally, and sales of marijuana are legalized federally, I guarantee you MC will lift this ban in a heartbeat so they can get a piece of that pie. Cannabis is a cash cow.