It turns out that if the campus police show up, they probably won't have warrants, and will just pound on your door for an hour or so. Turn out the lights and keep smoking.

At least here, the campus cops still have to go to a magistrate before entering without consent, and that's a bit of a treck.

This trick worked maybe half a dozen times before my old roommate was told that he'd be kicked off campus if he kept it up.