It's  not so much that university housing is exempt from the law, but that if there are policies which you have explicitly agreed to or are deemed (e.g. by agreeing to live there) to have agreed to and be bound by, those policies are enforceable. So if the housing policies say that a maintenance worker could enter without permission and you and your roommate, in one fashion or another, agreed to those policies (e.g. you had to agree to them to live there), then those policies are enforceable; in essence, you accepted a contract which lets maintenance enter at will.The best solution may be a chain, a deadbolt, or even a chair in front of the door when you want to make sure maintenance cannot enter like this again.