The real reasons explained:
Universities have their own police. Often they hire unarmed rent a cops. They are often worthless, just as worthless as the emergency phones/alarms that campuses have put out after a surge in rapes of female students. Likewise colleges/Universities are now going over to these digital emergency notification systems which are about as useful as the flow charts that many post in their classrooms telling faculty what to do in case of an emergency.
In America we use a “process” or some “system” to show action after a failure. Not that it would have prevented the event from happening in the first place, but at least it “shows action.”
What you will not see at US college campuses is armed faculty or selected students. Why? Because in all reality this is a liability issue. If a gunman comes on campus and kills 17 students the school isn’t liable, but if one college professor has an accidental discharge or loses a gun which the school sanctioned, that would put the school at risk. This isn’t an issue about safety, it’s an issue over who pays.
When my offspring started at an ostensibly Catholic university, there was a parents' orientation. The woman conducting it explained that drinking would absolutely not be allowed on the campus; and that students must be over 21 to drink off campus. However, there were co-ed dorms, girls and boys living on the same floor, and the RA's would explain to the kids about "sexiling" -- when the roommate leaves so their roomie can have sex with someone else in the shared room. Again, it comes down to liability. It's against the law for underage kids to drink, and if they do it in public the school is affected. But if someone's kid away from home for the first time gets pregnant, gets someone else pregnant or gets an STD or AIDS? That's a personal private family matter.
Ptooey.