While attending John Farnham's class a number of years ago, at Lake Tahoe, one of the California students related an incident that happened regarding a citizen who had an altercation in a bar, and his adversary pulled a knife on him.
The citizen said, "hey, I have a concealed weapons permit", which ended any assault. The Citizen was still in prison at the time of the class, after being convicted of, I believe, assault or brandishing, or both. The incredible thing is, the Citizen was NOT ARMED at the time.
Don't ask me how he could be convicted of a felony and go to prison. Nobody else knew, either, how something like that could happen.