What role do the rules of interpretation in Articles 31 and 32 of the Vienna Convention on the Law of Treaties (“VCLT”) have to play as potential agents of systemic integration and a coherent international legal system? Part of the answer lies in an examination of the practice of domestic courts which are increasingly called upon to undertake the task of interpreting treaties. This paper compares the practice of two superior courts – the Supreme Court of Canada and the High Court of Australia – in their approaches to the interpretation of international legal norms and their use of the interpretative principles in Articles 31 and 32. Despite the theoretical idea that the VCLT rules will, or should, encourage consistency of interpretation amongst varied interpreters, potential for divergences in interpretative technique (let alone outcome) remains. While both courts identify international law as a single system, and promote the role of Articles 31 and 32 as a means of ensuring uniformity of treaty application, historically the practise of the Supreme Court and High Court has been far from consistent, either internally or vis-à-vis each other. However, as the international law experience of these domestic courts grows, so too there appears to be an emerging consensus as to the preferred interpretative approach.
