Like any other institutions, international courts are both constrained and free, structured and open-ended in their production of legal outcomes. Yet, after decades of investigation, the driving forces behind international adjudication remain somewhat elusive. If international norms are textually indeterminate, then what guides their interpretation and application to concrete cases? To what systemic pressures are courts subject? And what forms of discretion do they enjoy? This chapter begins to answer these questions by focusing on the micro-level practices, relationships, and struggles of the legal experts populating international judicial institutions. On the one hand, these socio-professional dynamics are constrained by existing social arrangements, including the institutional design of courts, the networked interactions among individual actors, and the competent performances that punctuate the adjudicative process. On the other hand, existing social arrangements are open to contestation, renegotiation, and contingency, thereby creating opportunities for unorthodox and creative lawyering. As such, the socio-professional dynamics that take place inside international courts are both the vehicle of reproduction of legal outcomes and the source from which legal change originates.