The main problem with the notion of self-defense is it imposes on justice, for everyone has the right for a fair trial. Therefore, using a firearm to defend oneself is not legal because if the attacker is killed, he or she is devoid of his or her rights.
Now I remember back in my youth watching the cop TV show Baretta with it's classic theme song which had the line "don't do the crime if you can't do the time". It would seem to me that any criminal that commits a crime against another human being has to consider that his "time" could be spent in a small box six feet underground for eternity.
HuffPo: Shooting In Self-Defense Is Illegal Because It Denies Violent Criminals A Fair Trial