What is international humanitarian law?

International humanitarian law forms a major part of public international law (see opposite) and comprises the rules which, in times of armed conflict, seek to protect people who are not or are no longer taking part in the hostilities, and to restrict the methods and means of warfare employed.
More precisely, what the ICRC means by international humanitarian law applicable in armed conflicts is international treaty or customary rules which are specially intended to resolve matters of humanitarian concern arising directly from armed conflicts, whether of an international or non-international nature; for humanitarian reasons those rules restrict the right of the parties to a conflict to use the methods and means of warfare of their choice, and protect people and property affected or liable to be affected by the conflict .

Geneva and The Hague

International humanitarian law (IHL) also known as the law of armed conflicts or law of war, has two branches:

the law of Geneva, which is designed to safeguard military personnel who are no longer taking part in the fighting and people not actively involved in hostilities, i.e. civilians;
the law of The Hague, which establishes the rights and obligations of belligerents in the conduct of military operations, and limits the means of harming the enemy.

The two branches of IHL draw their names from the cities where each was initially codified. With the adoption of the Additional Protocols of 1977, which combine both branches, that distinction is now of merely historical and didactic value.

Who fights whom?

An international armed conflict means fighting between the armed forces of at least two States (it should be noted that wars of national liberation have been classified as international armed conflicts).

A non-international armed conflict means fighting on the territory of a State between the regular armed forces and identifiable armed groups, or between armed groups fighting one another. To be considered a non-international armed conflict, fighting must reach a certain level of intensity and extend over a certain period of time.

Internal disturbances are characterized by a serious disruption of internal order resulting from acts of violence which nevertheless are not representative of an armed conflict (riots, struggles between factions or against the authorities, for example).

Grotius and the law of nations

In current parlance, the law of nations is synonymous with the term public international law or international law, which is the body of rules governing relations between States and between them and other members of the international community.

Grotius, a jurist and diplomat, was the father of the law of nations. Following the Reformation, which divided the Christian church in Europe, he took the view that the law was no longer an expression of divine justice but the fruit of human reason and that it no longer preceded action but arose from it. Hence the need to find another uniting principle for international relations. The law of nations was to provide that principle. In his book De jure belli ac pacis, Grotius listed rules which are among the firmest foundations of the law of war.

Terminology

The expressions international humanitarian law, law of armed conflicts and law of war may be regarded as equivalents. International organizations, universities and even States will tend to favor international humanitarian law (or humanitarian law), whereas the other two expressions are more commonly used by the armed forces.