Treaty law and customary law are the main sources of international law. In the area of international humanitarian law, treaty law is well developed but its application is limited to States who have ratified the treaties in question, and to armed opposition groups within those States. The content of customary rules of international humanitarian law, on the other hand, is less clear because those rules are nowhere written down as such. Customary international law is created by a widespread, representative and uniform practice of States. Its content, as a result, must be determined on the basis of extensive research into State practice.

The study on customary international humanitarian law which the ICRC is currently finalizing is unique because such a study was never undertaken before. The Study has taken several years because of the extensive research involved but its outcome will be more than worth the wait. The study will provide the world with a common code of rules applicable to armed conflict, binding on all parties to armed conflicts.

This report is divided into three sections:

I. Origin of the Study
II. Organization of the Study
III. Purpose of the Study

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