I seem to recall a recent mock gunman that entered a college classroom and no one knew it was just a simulation. I can only imagine the outcome if lots of students and staff were allowed to carry guns. And let's not forget that just because someone hasn't committed a crime or been found mentally unstable doesn't mean they are going to be an outstanding citizen with a cun on them. "OOps! I just shot an innocent bystander by mistake! Oh dear! But, hey! I shot a criminal too! Yey!" Andrew