A crime against peace, in international law, consists of illegally starting a war. For committing this crime, the Nuremberg Tribunal sentenced a number of persons responsible for starting World War II. One consequence of this is that nations who are starting an armed conflict must now argue that they are either exercising the right of self-defense or the right of collective defense. It has made formal declaration of war uncommon after 1945.
In 1927, the Kellogg-Briand Pact, known as the General Treaty for the Renunciation of War, said:
The High Contracting Parties solemly declare in the names of their respective peoples that they condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy in their relations with one another.
To maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression or other breaches of the peace, and to bring about by peaceful means, and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace;
To develop friendly relations among nations based on respect for the principle of equal rights and self-determination of peoples, and to take other appropriate measures to strengthen universal peace;
The interdiction of aggressive war was confirmed and broadened by the United Nations' Charter, which states in article 2, paragraph 3 that
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.
Article 33
The parties to any dispute, the continuance of which is likely to endanger the maintenance of international peace and security, shall, first of all, seek a solution by negotiation, enquiry, mediation, conciliation, arbitration, judicial settlement, resort to regional agencies or arrangements, or other peaceful means of their own choice.
The Security Council shall, when it deems necessary, call upon the parties to settle their dispute by such means.
Article 39
The Security Council shall determine the existence of any threat to the peace, breach of the peace, or act of aggression and shall make recommendations, or decide what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security.
A crimeagainstpeace, in international law, consists of starting or waging a waragainst the territorial integrity, political independence or sovereignty of a state, or in violation of international treaties, agreements or (legally binding) assurances.
(c) The "sovereignty" rule means that it is a crime of aggression to use armed force with intent to overthrow the government of a state or to impede its freedom to act unhindered, as it sees fit, throughout its jurisdiction.
This definition of the crime of aggression belongs to jus cogens, which is supreme in the hierarchy of international law and, therefore, it cannot be modified by, or give way to, any rule of international law but one of the same rank.
A crimeagainst humanity is a term in international law that refers to acts of murderous persecution against a body of people, as being the criminal offence above all others.
The systematic persecution of African people by the South African apartheid government was recognized as a crimeagainst humanity by the United Nations in 1976.
For example, Nazi attempts to eliminate certain ethnic groups were recognized as having been crimesagainst humanity, yet Soviet persecutions of certain groups or terror bombing of the civilian population were not.