Is pot illegal in NY? It does happen to be in the state that I live in. If it is legal, then you can certainly feel free to debate with SU administration why they have a policy forbidding a legal substance. If not, It certainly seems reasonable to forbid/punish the use of an illegal substance. Especially when they are essentially a public representative of the University.
I'm not interested in debating whether or not it should be illegal. Honestly, I don't think it should. But if SU's code of conduct prohibits it, then it is on the player. As adult's we have to learn to play by the rules. They are adult's, it is time they learn the consequences of their actions. In many jobs, they would have lost their job. They are lucky, all they got was suspended.
I applaud the University for being proactive. If only it had originally been written sensibly and with clear guidelines, and top management had clearly supported and mandated its usage, no one would complain about its existence. But that is on the former top management, and I'm sure played a part in why they are no longer top management with the University.