What is International Humanitarian Law?
International humanitarian law (IHL) is a set of rules which seek, for humanitarian reasons, to limit the effects of armed conflict. It protects persons who are not or are no longer participating in the hostilities and restricts the means and methods of warfare. International humanitarian law is also known as the law of war or the law of armed conflict. International humanitarian law is part of international law, which is the body of rules governing relations between States.
International humanitarian law does not regulate whether a State may actually use force; this is governed by a distinct part of international law set out in the United Nations Charter.
Source: What is International Humanitarian Law? published by the International Committee of the Red Cross.