Customary Law: The ICRC Study
By Burrus M. Carnahan

In 2005, the International Committee of the Red Cross (ICRC) published a comprehensive study of the customary law of armed conflict. Based on ten years of work, the ICRC concluded that this body of law could be summarized in 161 rules. Due to the prestige of the Red Cross, and to the brevity and wide availability of the rules, the study is likely to become a valuable resource for those seeking an accessible summary of generally accepted rules of international law in armed conflict.

The report is published in three volumes, the first volume setting out the rules with commentary on each, and the final two listing the government practices on which the rules are based.

A notable feature of the study is the extensive treatment given to the role of customary law in non-international conflicts, where the reach of treaty law is much more limited than in conflicts between States. The study concludes that 149 out of the 161 rules identified apply in non-international armed conflict.

The ICRC’s endorsement of the report gives it authority, but the study has not been endorsed by governments. Although it is likely to be an influential assessment of the current state of customary international humanitarian law, it should not be taken as a definitive codification.