Why not just say: I'd like to bring into the campus a toy which is a replica of a Star Wars lightsaber... Is there any problem with that?
Just don't say anything. If someone asks, make something up like how you're part of a lightsaber group or something.
If it's a more risky item, well, that's your own discretion.
I find that in terms of a lightsaber, because it's so ingrained in our culture as a result of the popular movies which are nearly always quoted and referenced to in some form or another, they tend to be okay and even if they were considered a weapon, they're looked at so adoringly by the general populace that it almost completely get's overshadowed.
I'm not even lying. I brandished my saber with a friend of mine on a rather occupied and crowded bridge connecting two river-trails, because I kind of love attention and I love showing off stuff (yeah I'm full of my ego, haha). There were security guards nearby, but they paid no attention and everyone seemed to love it.
I guess they thought it was a staged-performance or something.
Additionally, I pulled this off multiple times while at a summer camp. Everyone loved it, especially the campers, and the staff had no problem with it.
So, I think it would be a lot easier to get away with this by saying it's for training than say if you had a 2nd generation, one-piece, hand-and-a-half Broadsword, but I digress.