If he really is "addicted", then the question probably needs to be - what is the problem that this addiction is the solution to?
I suspect that banning or otherwise preventing him from playing games is likely only to harden his position and make it more difficult to unravel what's going on, not to mention putting you into the role of enforcer/policeman rather than a more caring one.
In your shoes, I'd be trying to open up a discussion between equals, exploring with him what he gets out of the gaming (beyond "I enjoy it"), and what it helps him avoid. He may well not be happy in college, or (and I say this as a therapist who does some work with college students) is feeling like he has made the wrong choices/isn't getting on well with the subjects...in other words, the "addiction" is a compensatory activity aimed at making himself feel good at a time when it all feels fairly crap elsewhere.
Absolutely don't ban him from WOW, until he recognises he has a problem and starts asking you for help to deal with it. In the meantime, the best thing you can do is to set aside your panic about his future - if he's smart, he'll find a future anyway - and work at getting alongside him and achieving some kind of supportive alliance together. When he doesn't feel like you're judging him, policing him, or adopting some or other role that he perceives as hostile to his (present) interests, there's a chance that the pair of you will be able to work constructively together. Lower the boom on him, and you will just be another oppressor, out to make his life hard, and from which WoW is the only escape.
In my work, I often get very interesting results with what we tend to call "paradoxical interventions" - ie, doing the opposite, for good reasons, of what is expected of us. So I might point out that the kid who truants all the time (and is getting nothing but grief from everyone) is actually adopting a creative solution to a problem - "...so, what might that problem be?", and be able to engage in a constructive dialogue which, not unusually, makes the problem "just go away".
It may be that the solution in this case turns out to be him dropping out of college. That may feel enough like a catastrophe to him (not that he's likely to admit that at the moment) that he's ready to work constructively to avoid it, or at least find a decent Plan B, but all of the policing stuff will conveniently prevent him from having to address that - he can just focus on how fucking unfair it is (from his point of view) that as a nearly-adult, he's being babied by his parents, etc.
Sometimes we have to fail hard just to realise what it is we really want.