"Gun-free zones don't deter criminals-they help them by providing a guarantee that they will not face any armed resistance. But they do deter the law-abiding. A faculty member with a concealed-handgun permit who breaks the campus gun ban would be fired and likely find it impossible to get admitted to another school. Bringing a firearm into a gun-free zone can have serious adverse consequences for law-abiding people. But for someone like the Virginia Tech killer, the threat of expulsion is no deterrent at all."