International Judicial Monitor
Published by the American Society of International Law and the International Judicial Academy
September 2006, Volume 1, Issue 4

General Principles of International Law

Treaty Interpretation

Basic Rules

Articles 31 and 32 of the Vienna Convention on the Law of Treaties (VCLT) set forth the basic rules of treaty interpretation. The most fundamental rule is articulated in Article 31(1): "A treaty shall be interpreted in good faith in accordance with the ordinary meaning given to the terms of the treaty in their context and in the light of its object and purpose." Other provisions of Article 31 provide a specific definition of "context" and additional related guidance.

Types of evidence not referenced in Article 31—including the preparatory work of the treaty—are designated "supplementary means of interpretation" by Article 32. According to Article 32, such evidence may only be used in order to "confirm" the meaning that is suggested by an Article 31 analysis or in circumstances where application of Article 31 leads to an ambiguous or manifestly absurd result.

Schools of Treaty Interpretation

Notwithstanding the very specific hierarchy of relevant considerations laid out in Articles 31 and 32, there are discernable tendencies among different scholars—and even among different tribunals—to rely more heavily on one type of consideration than others in arriving at the final interpretation of a treaty provision.

There are at least three commonly acknowledged "schools" or approaches to treaty interpretation, which correspond to methods of construction of any legal text—including constitutions, statutes, and contracts. 

Textualist. The first school is textualism. All solid treaty interpretation begins with the words of a provision itself, as they are commonly understood. VCLT Article 31, in discussing treaty interpretation, calls for an examination of a text’s "ordinary meaning." Many treaties are drafted in two or more languages, and it is vital to ascertain not only which languages are "authentic," but also that there may be different shades of meanings of terms in different languages.

Intentionalist. Textualism can be a form of contextual reading of different provisions in a treaty text, in order to reach a sensible result. Already one can see a tension between the text of a treaty provision and the intent of the drafters. However, the second, intentionalist, approach to treaty interpretation has never been popular in international law. Indeed, the VCLT relegates sources shedding light on the intent of the drafters—including the negotiating history (known as travaux préparatoires, or travaux) of a provision—to a secondary role. They can be used only where the text is "ambiguous or obscure," or the plain meaning of the text leads to a "manifestly absurd or unreasonable" result.

One reason that travaux may be somewhat disfavored in international law is the concern that some countries might sign a treaty long after it was negotiated and signed. Should these newcomers be bound not only to the text, but also the informal understandings of the drafters? This would unduly privilege the interpretive positions of the original signatories. Likewise, use of negotiating history—including earlier drafts of a treaty, reports and commentaries, and diplomatic statements—can be selective and easily manipulated. Despite these cautions, use of travaux has become a constant feature of interpretive disputes over treaties.

Teleological. That leaves the third school of interpretation: seeking to effectuate the purpose of a treaty, rather than slavishly following the text or attempting to divine the intent of the drafters. Known in international law as a teleological approach, it can also be called purposivism. It is captured in the VCLT’s requirement that treaties be construed in light of their "object and purpose" and in view of "relevant rules of international law." The goal of this approach is to interpret a treaty in a way that gives scope to the fundamental reason or problem it was supposed to address. This approach is especially common with more "organic" or "constitutional" treaties, including those that establish international institutions (such as the United Nations Charter of 1945) or that fashion a "framework" for further international legislation.

There are limits to teleology in treaty construction, and interpreters cannot take the purpose of a treaty too far. For example, the International Court of Justice has flatly rejected the notion of "maximum effectiveness"— construing a treaty so as to give it the fullest effect. In a 1950 Advisory Opinion, the Court ruled that peace treaties concluded by eastern European states containing arbitration clauses could not be construed so as to give the UN Secretary General the power to appoint arbitrators, if the states themselves had refused to do so. 

Learn More

International Law:  A Handbook for Judges, David J. Bederman with Christopher J. Borgen and David A. Martin, (2003) 

Duncan B. Hollis, Merritt R. Blakeslee, L. Benjamin Ederington, Benjamin Ederington, National Treaty Law and Practice (2005)

Douglas M. Johnston, Consent and the Commitment in the World Community:  The Classification and Analysis of International Instruments (1997)

Jan Klabbers, The Concept of Treaty in International Law (1996)

A.D. McNair, The Law of Treaties (2d ed. 1961)

Shabtai Rosenne, Developments in the Law of Treaties, 1945-86 (1989)

Ian Sinclair, The Vienna Convention on the Law of Treaties (2d ed. 1984)

Mark E. Villiger, Customary International Law and Treaties (1997)  

This text has been from excerpted and adapted from International Law: A Handbook for Judges, ©2003 American Society of International Law.

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