I can't think of a show where the use of a firearm in self defense was actually shown to be within the law.
I remember an episode of LA Law in which a lawyer shot a guy in self defense. The matter was treated in a fairly serious and straight forward manner.
Then there is Denny Craine.
Sure if I took the time I'd remember several others.
But basically there isn't a show about self defense cases cause it'd be boring.