Jus ad bellum
Jus ad bellum, the law governing inter-state use of force, determines when one state may lawfully use force against another.
In accordance with the United Nations (UN) Charter and customary international law, there are two accepted exceptions to the general prohibition on use of force. One is when force is used in accordance with a UN Security Council resolution adopted under Chapter VII of the Charter, and the other is in self-defence against an armed attack. For self-defence to be lawful, use of force in response to an armed attack must be both necessary and proportionate.
Last updated on: 01 December 2013