A Study of the Issue of 'Relevant Rules' of International Law for the Purposes of Interpretation of Treaties under Article 31(3)(c) of the Vienna Convention on the Law of Treaties

The Vienna Convention on the Law of Treaties (VCLT) embodies Article 31(3)(c), prescribing that 'relevant rules' of international law must be taken into consideration while interpreting treaties, thereby promoting the idea of 'systemic integration'. The absence of the definition of 'relevant rules' has caused problems in treaty interpretation. International Courts and Tribunals have not provided adequate guidance on the consideration of rules of international law for treaty interpretation. The objective of the article is to study that part of Article 31(3)(c) which concerns 'relevant rules' in order to establish certain factors that must be taken into account for determining which rules of international law become relevant for the purposes of interpretation of a treaty. This will be done by examining the background of systemic integration and analysing cases in this area of law.