This also applies to the amateur student. For example, a Jiu-Jitsu student encounters an attacker who throws an unexpected punch, the Jiu-Jitsu student ducks under the punch and takes the assailant down to the floor. Then for good measure, they mount the attacker and apply a shoulder lock until they hear the wretched sound of torn ligaments. You are not justified to punish your attacker in any capacity. In this example you are obligated to walk away, if you can do so safely. Within the confines of a Jiu-Jitsu setting, that response would be given 6 points and a submission for the win. In real life you have a criminal and possible civil action.
Often people fail to realize that walking away from a bad situation has nothing to do with weakness, but rather everything to do with strength. We walk away not because we want others to realize our worth and value, but because we realize our own.
It should be the student’s instructors responsibility to inform their students of their respective states law on justifiable use of physical force in a self-defense situation.
I would be remiss to not inform you that I am not a lawyer (yet!) but rather a law student and BJJ enthusiast. Proper counsel should definitely be consulted on this issue and how it pertains to every martial arts school and instructor wherein.