Humanitarian law, more precisely international humanitarian law, is the branch of international law that regulates conduct during armed conflict in order to limit human suffering. It protects people who are not participating in hostilities or who are no longer participating, including civilians, wounded and sick combatants, prisoners of war in applicable international armed conflicts, and other persons placed hors de combat, while also restricting the means and methods that parties may use in warfare.
The ICRC identifies international humanitarian law as the law of armed conflict or law of war and explains that it consists principally of treaty and customary international law. The purpose is not to make war harmless or to decide which side has a morally justified cause. Instead, it establishes minimum legal constraints that apply once an armed conflict exists and seeks to reduce unnecessary suffering while recognising that hostilities occur.
The principal treaty foundations include the four Geneva Conventions of 1949 and their Additional Protocols, together with other treaties regulating particular weapons, conduct and protections, and customary international humanitarian law. Earlier Hague instruments also played a major role in codifying restrictions on the conduct of warfare. The historical development of the modern system accelerated during the nineteenth and twentieth centuries as states progressively codified rules concerning wounded soldiers, prisoners, civilians and methods of warfare.
The ICRC explains that international humanitarian law has older customary roots but that the Geneva and Hague Conventions became central examples of modern codification. The terminology law of war and law of armed conflict remains widely used, although international humanitarian law is the preferred term in many contemporary legal and humanitarian contexts.
A foundational principle is distinction. Parties to an armed conflict must distinguish between civilians and combatants and between civilian objects and military objectives when conducting attacks. Other central principles include proportionality in attack, precautions to reduce civilian harm, the prohibition of certain forms of treatment and the requirement to treat persons in protected categories humanely.
The ICRC identifies distinction, protection of persons hors de combat, prohibition of unnecessary suffering, necessity and proportionality among the fundamental principles derived from the structure of international humanitarian law. These principles do not mean that all civilian casualties automatically establish a violation. Legal assessment depends on the circumstances, the target, the information reasonably available to the attacking party, the expected military advantage, feasible precautions and the applicable rules.
International humanitarian law applies to international armed conflicts and non international armed conflicts, but the precise rules applicable can differ according to the classification and circumstances of the conflict. The ICRC distinguishes international armed conflicts involving two or more states from non international armed conflicts involving governmental forces and organised non governmental armed groups or such groups among themselves. Classification is a legal question based on facts rather than simply the political description used by participants. The existence of an armed conflict triggers the relevant body of humanitarian rules. Humanitarian law can therefore apply regardless of whether a government formally declares war. The legal classification can evolve if circumstances change, which is why factual developments can alter the applicable framework.
Humanitarian law must be distinguished from the international law governing whether a state may lawfully use force in the first place. The ICRC describes the distinction through the concepts jus ad bellum and jus in bello. Jus ad bellum concerns the legality of resorting to force, whereas international humanitarian law governs conduct once an armed conflict exists and is not dependent on deciding which side had the legally justified reason for starting the conflict.
This separation is fundamental because humanitarian protection would be weakened if the treatment of civilians or prisoners depended on determining which party was morally or legally responsible for initiating the conflict. A party can therefore have a disputed or unlawful basis for resorting to force while still being bound by humanitarian rules governing how it conducts hostilities.
Humanitarian law regulates both protection and methods of warfare. Protective rules address people affected by conflict, including wounded and sick persons, detainees, prisoners of war where applicable, civilians and humanitarian personnel. Conduct rules regulate attacks, targeting, precautions, weapons and treatment of persons under the control of a party. Some weapons are restricted or prohibited through specific treaties and customary rules.
The law also contains rules concerning humanitarian relief, occupation, treatment of detainees and protection of cultural or civilian objects under applicable circumstances. Humanitarian law does not prohibit all military action and does not require combatants to avoid every military risk. Its function is to establish legally enforceable limits within the reality of armed conflict, balancing military considerations with humanitarian constraints.
Enforcement of humanitarian law operates through several mechanisms. States have obligations to respect and ensure respect for applicable rules, and domestic legal systems can prosecute certain serious violations. International criminal law also provides mechanisms for prosecuting specified international crimes under particular jurisdictional conditions. States can investigate alleged violations, military justice systems can apply relevant rules, and international or hybrid courts may have jurisdiction in appropriate circumstances.
The ICRC promotes respect for humanitarian law and works to disseminate and develop understanding of the rules, but it is not itself a general international criminal court. Enforcement therefore depends on a combination of domestic legislation, investigations, prosecutions, international mechanisms, diplomatic action and institutional monitoring.
Humanitarian law is consequently a specialised legal framework for armed conflict rather than a general code of morality about war. It seeks to protect people affected by conflict and limit the means and methods of warfare while leaving separate questions about the legality of resorting to force to other areas of international law. Its principal sources include treaties and customary international law, and its detailed operation depends on the type of conflict and factual circumstances. The central concepts of distinction, proportionality, precautions, humane treatment, military necessity and protection of persons hors de combat provide the structure for understanding its operation.
