The Practicians

Abstract This chapter reviews the dominant approach in which customary international law gets in validity, its legality, its consistency, and its factuality from practice and opinio juris. It investigates the presumptive character of the moment where practice and opinio juris coalesce and generate customary international law, which must be ascribed a genitor. It also emphasizes that as long as practice and opinio juris have a sufficient number of genitors, they can be conducive to the formation of customary international law. The chapter talks about practicians as the genitors of the practice which customary international law must emanate from, such as those that produce the actual behaviours (practice sensu stricto) and the beliefs (opinio juris) that are generative of customary international law. It outlines the determination of the practicians of customary international law as a discursive performance that is commonly and repeatedly witnessed in debates about customary international law.