The law of armed conflict (also called the “law of war”) can be divided into two categories. The first concerns the legitimate reasons for starting a war, known by its Latin terminology, ius ad bellum. The laws during war, ius in bello, are also called international humanitarian law.
- Ius ad bellum. Article 2(4) of the UN Charter states, “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.”4Some regard this as the prohibition of the use of force outside of UN-approved actions. On the other hand, others consider this clause only non-binding rhetoric, especially considering the history of armed conflict since the UN’s birth in 1945.The UN Charter and CIL do recognize that a state is entitled to use force without international approval when it is acting in self-defense. However, the events that trigger this right to self-defense are subject to debate. Most international lawyers agree that self-defense actions must be immediately necessary and proportional to the attack the state is trying to repel. In this era of terrorism and weapons of mass destruction, some contend that legal self-defense also extends to pre-emptive attacks to prevent the development of a military threat.
- Ius in bello. Once armed conflict has begun, international humanitarian laws begin to apply. Some of the most important principles of ius in belloare that there must be a valid military purpose to every attack (“military necessity”), that attackers must try to avoid killing non-combatants (the principle of “distinction” between military and non-military targets), and that if non-combatants are killed, their deaths must be in proportion to the military necessity of the attack (“proportionality”).For example, attacking a weapons factory is legitimate, but if the factory is located near civilian homes, then the attacker must try to avoid attacking those home; if attacking them will inevitably kill many civilians, the attack should not take place.Applying these principles in practice, however, is very difficult. Who determines whether an attack was necessary, distinguished between civilians and combatants, and was proportional? The main rules governing ius in bello are written down in the
For more information on the Geneva Conventions, click here.