I think you do.This is a hypothetical situation.
You find yourself alone on a uninhabited,unknown,ungoverned island.
A bad person lands and has tried to kill you.
Do you have a right to kill this person?
From where does this right arise?
My position would be that God created us with the innate need for self-preservation.
Of course, after the event the survivor could vote to pass a law authorizing such acts as he previously committed. There'd be no opposition vote. Heck- he could even hold a trial.