An Exploration on Applying and Clarifying International Customary Law in the Jurisprudence of ICTY and ICTR

 International custom, besides treaties, is the principal source of international law among its formal sources. Furthermore, judicial decisions in general and the jurisprudence of international courts and tribunals in particular, along with the teachings of the most prominent international jurists, form the subsidiary sources of this branch of law the function of which is to ascertain the existence of legal rules and determine their scope of application. Accordingly, it could be argued that on the one hand, international custom is one of the main sources of international courts/tribunals and on the other, international courts/tribunals define and clarify the scope of customary rules in their judicial decisions. In this regard, the jurisprudence of two international tribunals namely International Criminal Tribunal for Former Yugoslavia (ICTY) and International Criminal Tribunal for Rwanda (ICTR), in addition to applying international customary law for the issuance of their judgments, have played a notable role in clarification of some customary rules. Therefore, exploring the performance of these two tribunals as to the application and clarification of international custom seems to be profitable. The reason and cause for choosing the jurisprudence of these two tribunals is the ambiguity in applicability of treaty law in the course of trials and consequently increasing reference to international custom and their notable position in International Criminal Law as well. The first section of the article is describing the legal sources of the tribunals with emphasis on international custom. Second section entails analyzing the approach of these tribunals regarding two-element theory of international customary law. Thereafter, the content of international customary law would be studied in terms of its jurisdiction and nature. Finally, the article ends with concluding remarks. The present study which is a mixture of translation and research, through a descriptive-analytic method, attempts to deal with the application and clarification of international customary law in the jurisprudence of ICTY and ICTR.