Abstract: International law has always been contested. In recent years, however, competition between States to influence the trajectory of international law has intensified. Unfortunately, most international lawyers and policy makers still employ an impoverished understanding of the way in which international law is created (i.e., through formal international negotiations or as developed through custom). In this article, I argue that this formalist perspective neglects the foundational role of domestic lawmaking and regulation in the development of international law. Indeed, this paper shows that domestic action has historically been a direct causal antecedent to international legal regimes, and concludes that States must fundamentally reconsider the underpinnings of international law if they hope to effectively advance their national interests in international politics. These findings are born out through four case studies, which analyze the development of international legal regimes for the continental shelf, bribery of foreign officials, data privacy, and artificial intelligence. In each case study, I apply an analytic model rooted in Aristotelian understandings of causation, and expanded upon through the constructivist legal literature. Throughout, the paper provides concrete suggestions as to how States can re-imagine their approach towards international law to better advance their interests in the increasingly fragmented, yet still highly interconnected, world of international politics.