The story finally gets to the interpretation and application of legal norms to the facts of the case. This chapter deals with the first interpretive step, called law-ascertainment, where the interpreter identifies the rules that are relevant to the case at hand. Donning the hat of an explorer, the interpreter maps the body of norms precedents in concentric circles – starting with the sources closest to the centre of gravity of their judicial regime and gradually venturing into more peripheral territory. The results of these practices explains the degree of cohesion or fragmentation in international law. As the legal system grows more complex, interpreters no longer have time and resources to master it all, and prove increasingly partial and selective in their legal readings. The emergence of self-contained regimes is largely due to epistemic constraints which, in turn, reflect the social structures of the international judicial community.