In my opinion, our student workers are neither trained nor paid to be the responsible staff for the entire library. That's a staff responsibility and I'd be sure we have staff members all the time (but of course during these days of budget cuts using student workers seems so appealing, of course that arguement could be used to replace all staff if you're not concerned about their level of traiing and responsibility).
Campus security folks should be called in if there's a real security problems.
