International Humanitarian Law is the body of international rules designed for armed conflict that limits the effects of warfare for humanitarian reasons, protects people who are not or are no longer participating directly in hostilities and restricts the means and methods by which parties may conduct hostilities. It is also called the law of armed conflict or, historically, the law of war. The ICRC identifies IHL as a branch of Public International Law consisting primarily of treaty and customary rules. IHL therefore does not abolish armed conflict but establishes legal constraints that apply when the factual and legal conditions for an armed conflict exist.
IHL applies to armed conflicts rather than to every situation of political violence. The legal classification of a situation matters because different rules can apply to International Armed Conflicts and Non International Armed Conflicts. The ICRC explains that International Armed Conflicts involve two or more states using armed force against each other, while Non International Armed Conflicts involve qualifying confrontations between governmental forces and organised armed groups or between such groups. Importantly, IHL does not depend simply on whether governments formally declare a war. Its applicability is determined by the facts and the legal criteria governing armed conflict.
The Geneva Conventions of 1949 form the foundation of modern IHL, supplemented by Additional Protocols and other treaties and customary international law. The rules protect categories including wounded and sick persons, prisoners of war and civilians, while regulating conduct during hostilities. Historically, scholars sometimes distinguished the law of Geneva, concerning protection of victims, from the law of The Hague, concerning conduct and methods of warfare. The ICRC explains that the later development of Additional Protocols combined aspects of these traditions, making the distinction mainly historical and analytical today.
A central principle of IHL is distinction, requiring parties to distinguish between civilians and combatants and between civilian objects and military objectives. Related principles restrict attacks that are expected to cause excessive incidental civilian harm in relation to the anticipated concrete and direct military advantage and require feasible precautions in attack. IHL also prohibits certain methods and means of warfare and requires humane treatment of persons who are in the power of a party and protected by the relevant rules. These principles attempt to balance military necessity with humanitarian considerations rather than prohibit all military action.
IHL applies to all parties to a qualifying armed conflict regardless of the legal justification for beginning the conflict. This distinction is crucial. The question of whether a state was legally entitled to use force against another state belongs principally to the rules concerning the use of force under the United Nations Charter and related international law. IHL instead governs how parties conduct themselves once an armed conflict exists. The ICRC explicitly distinguishes jus ad bellum, concerning resort to force, from jus in bello, concerning conduct during armed conflict.
IHL imposes obligations on states and, in applicable circumstances, on organised armed groups and individuals. Serious violations can constitute war crimes where the relevant legal requirements are satisfied. National courts, international courts and other mechanisms can contribute to enforcement, although the specific jurisdiction depends on applicable law. IHL also imposes duties concerning dissemination, training and national implementation. The legal framework therefore operates through both international rules and domestic mechanisms. Compliance cannot depend solely on battlefield decisions because states and armed groups must organise institutions and training capable of translating legal obligations into operational practice.
IHL is closely related to human rights law but the two bodies of law are not identical. Human rights law generally protects individuals through a broader framework that operates in peacetime and during emergencies, subject to applicable limitations and derogation rules. IHL is specifically designed for armed conflict and regulates conduct of hostilities and protection of persons affected by conflict. The United Nations describes international human rights law and IHL as complementary components of a wider framework protecting life, health and dignity. Their interaction can therefore be legally complex in situations involving detention, occupation, use of force and civilian protection.
International Humanitarian Law remains significant because contemporary conflicts can involve states, organised armed groups, multinational forces, proxy relationships, urban warfare and changing technologies. The ICRC's 2024 analysis emphasises that classification can become complex where coalitions, support relationships and multiple armed actors are involved. The fundamental purpose nevertheless remains constant: armed conflict does not create a legal vacuum. IHL establishes minimum humanitarian constraints on warfare, protects people who are not or are no longer directly participating in hostilities and limits methods and means of warfare even when the broader political dispute remains unresolved.
