I have noticed that most often, when one defends their life, even though they comitted a crime by having a weapon illegaly concealed they are not chraged with the crime.
Think back to the shooting at the school dance in PA a few years back. A teacher ran to his car, off campus, to retrieve his gun. He subdued the shooter and was praised as a hero. Some started making rumblings about his bringing a firearm onto school grounds, a gun free zone. The police told those asking for prosecution to stuff it.
In their haste to relieve citizens of their right to self defense, politicians have made them victims of those who do not care if they break the law.
The "Gun-Free Zone" sign is about as effective in protecting against school violence as an amulet is in warding off the Black Plague.