The fact that marijuana is still federally classified as a Schedule I drug. Why would you think credit card companies should allow cardholders to make illegal transactions using their credit cards? Do you think they'd be okay with people using their credit cards to purchase child pornography? Or hitmen? Trafficked persons? What about 100 kilos of cocaine? I'm aware marijuana isn't as bad as any of those things, and it's way past time for the laws to be updated, but the fact remains it's still against the law to purchase it. To argue they have no obligation to make sure they aren't facilitating in illegal actions is absurd. As far as I know they've never allowed illegal transactions to be made, so absolutely no precedent is being set here.