On 17 March 2005, the President of the International Committee of the Red Cross (ICRC), Jakob Kellenberger, presented a study (hereinafter “the Study”) of customary international humanitarian law (IHL). A decade earlier, the International Conference of the Red Cross and Red Crescent had mandated the ICRC to “prepare […] a report on customary rules of IHL applicable in international [IAC] and non-international armed conflicts [NIAC], and to circulate the report to States and competent international bodies.” The Study's objective was to capture a “photograph” of the existing, hitherto unwritten rules that make up customary IHL. Comprehensive, high-level research into customary IHL followed; the end result of which is undeniably a remarkable feat and a significant contribution to scholarship and debate in this area of international law.