Crime Against Peace

A crime against peace, in international law, refers to "planning, preparation, initiation, or waging of wars of aggression, or a war in violation of international treaties, agreements or assurances, or participation in a common plan or conspiracy for the accomplishment of any of the foregoing". This definition of crimes against peace was first incorporated into the Nuremberg Principles and later included in the United Nations Charter. This definition would play a part in defining aggression as a crime against peace.

An important exception to the foregoing are defensive military actions taken under Article 51 of the UN Charter. Such defensive actions are subject to immediate Security Council review, but do not require UN permission to be legal within international law. "Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations." (UN Charter, Article 51) The Security Council will determine if the action is legally the "right of individual or collective self-defence", or it may appoint another UN organ to do this.