These terms are more commonly and properly used to refer to the policies governing weapons use by law enforcement agencies. There are major differences between how the police and military use force. A police officer operates on a continuum of force using the minimum necessary that is appropriate in the circumstances. A police officer cannot kill someone simply because they are a criminal. In contrast, military personnel can use deadly force against anyone who is an enemy combatant.
Military forces have no obligation to try to capture or wound, rather than kill, an enemy.
It is - sort of. All Members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered. All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations. Measures taken by Members in the exercise of this right of self-defense shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security. Nothing in the present Charter precludes the existence of regional arrangements or agencies for dealing with such matters relating to the maintenance of international peace and security as are appropriate for regional action, provided that such arrangements or agencies and their activities are consistent with the Purposes and Principles of the United Nations.