The Geneva Conventions were adopted 60 years ago. Today, they are universally ratified. Notwithstanding their universal adherence as treaty law, the customary nature of the provisions of the Geneva Conventions remains relevant. This article examines the claims that the Geneva Conventions, in general, are part of customary international law. Beyond this level of generality, it argues that the grave breaches regime is part of customary international law, including the definition of the grave breaches as well as the procedural rules governing grave breaches. The latter include the obligation to enact effective penal sanctions in domestic law and the obligation to search for and to try or extradite persons suspected of grave breaches on the basis of universal jurisdiction. The article argues that these rules are not simply "technical' rules but are "fundamental to the respect of the human person and [humanity]', a phrase used by the International Court of Justice when examining the customary nature of the Geneva Conventions.