I've been trying to get people to listen to me on this subject for years. I can remember when Kennesaw passed the law and how dramatically crime dropped in the city. I live on the other side of Atlanta from Kennesaw and in my area, everyone knows that almost everyone has guns. We have very little crime while the two closest cities are no safe to go into at night.
They don't actually enforce the law in Kennesaw but just knowing that the chances are very high, someone is going to have a gun nearby, is enough to prevent most would be criminals from choosing to commit crimes there.