Question of the Day

The university has a post office (contract unit) in the student union. In addition to being able to buy stamps and ship parcels, one can also rent post office boxes[1].
Now, it’s perfectly legal to ship firearms in the mail (handguns must be shipped by an FFL through the mail, mere mortals can only ship long guns) so long as certain rules are obeyed. Parcels, including firearms, which are too large to fit into a box are held for the box holder to collect over the counter.
Now, it’s legal to mail firearms, and it’s legal to receive firearms (say, being returned from the manufacturer for service, or from a gunsmith). It’s legal to possess firearms just about anywhere in Tucson, but it is against the law to possess firearms on the university campus without the express permission of the university police department (good luck getting such permission).
Assuming one were to have a PO box at the on-campus post office, and one was to receive a firearm…would it be legal to transport that firearm (unloaded, cased, locked, etc.) from the on-campus post office to an off-campus location by the most immediate means available (e.g. walking off-campus, to a waiting car, etc.)? It seems like there’s some sort of “island of legality” within the confines of the post office, but one cannot actually transport the firearm from the post office to an off-campus location without crossing through the no-guns-allowed region of the campus itself.
Any thoughts or pointers? I could call the university police department, but I figured I’d ask here first.
[1] Which reminds me of a cool label I saw affixed to a liquid nitrogen dewar (like a big thermos) today: it was made by some nuclear division of the Union Carbide Company, and had “Post Office Box X” in some city. How cool is that? “Box X” sounds very mysterious indeed, particularly when relating to nuclear stuff.