International humanitarian law (law of war) is a field of international law regulating armed conflict between states and, more recently, between states and informal groups and individuals. This field of international law is one of the oldest fields of conventional international law. Its core principles were established first in the Geneva Convention of 1864 and then expanded in the Geneva Conventions of 1949.
International humanitarian law governs the legality of justifications for war (jus ad bellum, or when states can resort to war) and the legality of wartime conduct (jus in bello, or how states must behave themselves during the war). Moreover, international humanitarian law protects people:
- Who are not part of the conflict, or
- Who have ceased to participate in the fighting (injured and ill, doctors, prisoners of war, and civilians).
International humanitarian law also prohibits combatants from employing weapons or strategies that cause needless harm to their adversaries.
Some relevant prohibitions established in international treaties of humanitarian law are related to the use of the following weapons and methods of warfare:
- Poison weapons
- Cluster munitions
- Explosive and inflammable projectiles, which depend on the weight
- Laser weapons
- Biological weapons
- Chemical weapons
- Pillaging property
- Denying quarter
- Starving the population
International humanitarian law does not apply to instances of violence and internal unrest that do not meet the criteria of an armed conflict. Instead, these cases are governed by national and human rights laws.
[Last updated in May of 2023 by the Wex Definitions Team]