My university banned guns on campus just before I enrolled. They must have talked with my friends behind my back.
As it turns out though, Texas says it's legal to have firearms on a college campus, even one where the school bans them. So I can legally keep my firearms in my vehicle parked on the street or in the parking lot, I just can't bring them onto the campus lawn or into a building without written permission (and what are the odds of getting that permission?).
Otherwise, a "don't get caught" and "what I don't know can't hurt you" unspoken policy exist. In fact, the guy who was my RA last year and is now the head RA for the dorm made an agreement with me: neither of us would rat the other out if we found a gun in the room. He's now planning on buying an SKS online and keeping it in a locking case from Wal-Mart in his closet. He figures if somebody finds the case, they can't open it to see what's inside, so his ass is still covered.
About half the trucks on campus have a rifle or shotgun hidden behind the seat for target shooting, dove season, and deer season, and I know of a few guys who carry concealed handguns (with a CCW or not, I don't know and don't want to know) on campus. And these are responsible, (normally) law-abiding people, not thugs and gang-bangers, so I'm not overly worried about them.
I did have an RA recently ask me whether or not I had guns for "all the ammo you got there" (mostly empty casings kept as souvenirs and a couple live rounds, less than a dozen total) when he did a room inspection. I asked him, "did you see any guns when you came in?" "No." "Then we're cool." He just shook his head at me, checked my room off the list, and walked out.