I'm not even close to being a lawyer, and I'm very much NOT familiar with the specifics in your case, but two things come to mind from what you've posted...
Firstly, I would agree that an unloaded boomstick, ideally cased in a locked vehicle, should be safe and clear.
Secondly, a loaded magazine carried on your person is NOT a weapon/firearm/etc. so I would just carry that with me while the rest is in the car. When you return to the vehicle, get yourself to a legal location, and lock and load =)
As an aside, that kind of BS is why I'm kinda glad I wasn't into firearms during my 'college' years, and I'm even happier that I never attended a major university where such policies apply. As if they don't already do everything to indoctrinate people =)