The Vienna Convention on the Law of Treaties 1969 (VCLT) sets out the principal rules for treaty interpretation in international law. Articles 31 to 33 codify customary rules that guide how treaties should be understood. This essay examines these provisions and considers whether they require improvement. It draws on the text of the Convention itself and relevant commentary to assess both their strengths and limitations from the perspective of public international law.
The General Rule of Interpretation under Article 31
Article 31 establishes the general rule that a treaty must be interpreted in good faith according to the ordinary meaning of its terms in their context and in light of the treaty’s object and purpose. Context includes the preamble and annexes, along with any agreement or instrument made in connection with the conclusion of the treaty. Subsequent agreements between the parties and subsequent practice may also be taken into account, as may relevant rules of international law. This holistic approach seeks to balance textual fidelity with teleological considerations. However, the reference to “object and purpose” can introduce uncertainty, as different states may advance competing understandings of a treaty’s aims (Aust, 2013).
Supplementary Means under Article 32
Article 32 permits recourse to supplementary means of interpretation, including the preparatory work of the treaty and the circumstances of its conclusion. These materials may confirm the meaning derived from Article 31 or resolve ambiguity or absurdity. The provision reflects a cautious approach that treats travaux préparatoires as secondary rather than primary sources. While this hierarchy promotes stability, it can disadvantage states that were not involved in the drafting process, since access to preparatory records is often uneven (Sinclair, 1984).
Interpretation of Multilingual Treaties under Article 33
Article 33 addresses treaties authenticated in two or more languages. Unless otherwise provided, each text is equally authoritative. Terms are presumed to have the same meaning in each authentic text, and any divergence is resolved by applying Articles 31 and 32. This rule recognises the practical reality of multilingual diplomacy yet may generate difficulties when linguistic nuances produce materially different interpretations. The presumption of equivalence does not always reflect the complexities of translating legal concepts across languages (Shaw, 2017).
Potential Improvements to the Rules
Critics argue that the VCLT framework could be improved through greater clarity on the weight to be given to subsequent practice and through more explicit guidance on the use of travaux préparatoires in disputes involving non-participating states. Some scholars also suggest that additional rules addressing the role of soft-law instruments in interpretation would better reflect contemporary treaty-making (Gardiner, 2015). Nevertheless, the existing provisions have proved durable and are widely accepted as reflecting customary international law. Any reform would require broad consensus among states and might risk undermining the predictability that the current rules provide.
Conclusion
The rules contained in Articles 31 to 33 of the VCLT offer a structured yet flexible framework for treaty interpretation. While they display certain limitations, particularly regarding the concept of object and purpose and access to preparatory materials, they remain central to the practice of international law. Limited refinements might enhance clarity without sacrificing the balance achieved in 1969.
References
- Aust, A. (2013) Modern Treaty Law and Practice. 3rd edn. Cambridge University Press.
- Gardiner, R. (2015) Treaty Interpretation. 2nd edn. Oxford University Press.
- Shaw, M.N. (2017) International Law. 8th edn. Cambridge University Press.
- Sinclair, I. (1984) The Vienna Convention on the Law of Treaties. 2nd edn. Manchester University Press.
- United Nations (1969) Vienna Convention on the Law of Treaties. United Nations Treaty Series, vol. 1155, p. 331.
