Not going to argue about whether or not it’s constitutional (because I don’t know), but I just wanted to point out that this case is slightly more complicated than just “you’re not allowed to purchase”. It’s “you’re not allowed to purchase… BUT other people are”. Which means it’s potentially a question of discrimination, which is maybe not as cut-and-dry as a “normal” law banning a substance across the board.
You sound like someone I know who insists that the probability of anything happening is always 50/50, because “either it happens or it doesn’t”.