The jurists believe that a person in a state of nature must control himself to conform to that which is proper for a defense, that is moderamen inculpatae tutelae. That means simply that without necessity I should not use the most extreme violence when a lesser degree of force can be employed. That is correct according to laws of ethics. According to strict right and justice, I can never be limited when someone threatens to kill me. According to natural law, I am not bound to use lesser force, and, therefore, moderamen inculpatae tutelae does not apply. But in civil society the principle is valid since the state can require that I have a duty to not injure other persons.  If, however, my life is possibly but not certainly in danger the state cannot promulgate a law that requires that I exercise  a limited defense since the most severe punishments the state can render are not greater than the evil that I face.  The law, therefore, cannot restrict my defense. Such a law would be absurd.