jus ad bellum

Jus ad bellum deals with the legality of going to war. Under the UN Charter, Article 2(4) prohibits the threat or use of force against the territorial integrity or political independence of any State. There are two accepted exceptions: individual or collective self-defence against an armed attack (Article 51), and enforcement action authorised by the Security Council under Chapter VII.

It must be kept separate from jus in bello, which governs how hostilities are conducted once they begin. A State fighting a lawful war of self-defence must still obey the laws of war, and the laws of war protect both sides equally whether or not the war was lawful.

Example

Whether the invasion was justified as self-defence under Article 51 is a question of jus ad bellum, not of humanitarian law.

In Indian law

• Articles 2(4) and 51 and Chapter VII, Charter of the United Nations, 1945

See also

jus in bello · casus belli · responsibility to protect · jus cogens

Read more in the study notes

• Duties, safety, health and welfare under the OSH Code (Labour and Industrial Law II)
• The British executive: the Crown, the monarch, the Prime Minister and the Cabinet (Political Science - Major World Governments)