The laws in question aren't there to legislate/regulate the psychos, but to lay blame on the administrators of the school should the psychos do something. Since the administrators haven't got anywhere near the resources it takes to detect and deter individual carry, they are compelled to impose zero tolerence policy. This very generalized policy does nothing to prevent the psychos from doing what they are going to do, because the administrator still doesn't have the resources he needs to enforce the policy completely. However, it does limit his culpability in court or before his superiors by allowing him to claim they did everything "within his power" to prevent such an event. Unfortunately, that means then they have to enforce the zero tolerance policy any and every time an event that meets the generalized criteria occurs, otherwise they risk re-assuming culpability.

We have an almost uncountable number of such regulations/laws on the books that have no effect on stopping willful acts of violence, but hold those in authority accountable for the acts of psychos, unless they exercise "due diligence".

Ain't our legal system great?!!!