Legitimacy Audiences, Communities of Practices, and the Interpretive Practices of International Criminal Courts

International courts have considerably altered legal provisions in international criminal law, to the extent of potentially making new law. While recent scholarship on international judicial law-making and legitimacy has mainly focused on the potentially resulting democratic deficit, only few empirical analyses of how international criminal courts legitimise their decisions exist. Using practice theory, this paper argues that international and hybrid criminal courts have relied on references to a broad set of legal sources of authority to legitimise their interpretations of legal provisions. The sources cited in practice, however, differ substantially from a formal legal view of the sources of international law and frequently include, for example, judicial decisions and academic writings. This paper suggests that reference to less formal sources addresses a specific legitimacy audience of legal experts. It combines elite interviews with judges and legal officers with a quantitative analysis of cross-references used by the ICC, the ICTY, the ICTR, and the SCSL when interpreting the law of war crimes and the crime of genocide. Challenging conventional legal accounts of international law, the paper concludes by using its empirical findings to explore the conceptual traction that can be gained by examining how legitimacy audiences and communities of practice overlap.