This paper analyses the defining features of legal translation in the development of international and supranational law, taking a comparative approach between different organisations, particularly the United Nations, the World Trade Organization, the European Union and their respective adjudicative bodies. The scope and communicative conditions of legal translation in such settings are first described, including processes of lawmaking, law application and adjudication. In the legal contextualisation of translational action, emphasis is placed on the interconnection between different sources of law, the hybridity of legal texts and discourses, and the interplay between international and national levels of rulemaking and enforcement. The challenges encountered by the translator in the search for maximum accuracy are then reviewed with a focus on terminological problems, quality assurance and ambiguity. Finally, the examination of linguistic concordance in adjudication procedures further highlights the special contribution of legal translators to the functioning of each international or supranational legal order, and recommendations are made to better acknowledge and benefit from this contribution.