Custom and Adjudication in International Law through the Civil Law Tradition in Colombia

International Law has often been described as a decentralized domain, in the sense that the authority to create the law doesn’t derive from a sole center of power. This is especially true in the context of normative production through Customary International Law. Multiple and disaggregated expressions of state practice and opinio iuris come together in the formation of custom, and a variety of actors, which authority is often contested, including international organizations and tribunals, play a major role in identifying the rules of customary law. One could also speak of decentralization, or at least of non-systematization, in the domain of international adjudication. Most international judicial bodies and arbitral tribunals decide the disputes brought before them under the formal rule that their decisions only produce effects between the parties to the case. However, in practice, it is not rare to see forms of cross-referencing among international decisions that have rightfully made many legal scholars argue about the existence of a system of jurisprudence both in the case of the International Court of Justice as a prominent example of a permanent international court and arbitral awards. In this essay, I address these issues, namely, the structures that govern normative production through Customary International Law and the criteria to determine the authority of international judicial decisions and arbitral awards by reference and comparison to the structures and criteria employed for the same purpose in the national level in Civil Law jurisdictions, where, as we will see, legal production is regulated and mostly tied to the centralized authority of the state and one can more properly speak of systems of jurisprudence, with exceptions in the domain of domestic arbitration. Drawing from my background and experience, I engage in this comparative analysis based on an account of the General Theory of Law in the Civil Law tradition with examples of legal developments and attributes from the Colombian legal system. I conclude by offering some comments on the most salient points of comparison between the domestic and international levels. The Essay is also thought to serve as a legal thought comparative companion for students formed in the Civil Law to engage in the study of two of the most important sources of International law: custom and adjudication.