Considering the fundamental role of treaties in international relations and recognizing the importance of treaties as a  source of  international law, the Vienna Convention on the Law of Treaties was adopted in 1969. The Vienna Convention on the Law of Treaties regulates the conclusion and entry into force of treaties, the application and interpretation of treaties as well as the amendment, invalidity and termination of treaties. According to Article 2 of this multilateral agreement, a 'treaty’ means 'an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation.’ A treaty concluded between one or more States and one or more international organizations, or between international organizations, can also be referred to as a treaty. According to Article 38 of the Statute of the International Court of Justice, 'international conventions, whether general or particular, establishing rules expressly recognized by the contesting states' must be applied by the Court, when deciding disputes that are submitted to it. From this one can conclude that treaties are one of the principal sources of public international law.

If you want to read (or download) the substance of a particular Treaty directly, please visit this database, provided by Oxford University Press.

This Research Guide is intended as a starting point for research on the Law of Treaties. It provides the basic legal materials available in the Peace Palace Library, both in print and electronic format. Handbooks, leading articles, bibliographies, periodicals, serial publications and documents of interest are presented in the Selective Bibliography section. Links to the PPL Catalogue are inserted. The Library's systematic classification index subject: 'Treaties' and subject heading (keyword) Treaties are instrumental for searching through the Catalogue. Special attention is given to our subscriptions on databases, e-journals, e-books and other electronic resources. Finally, this Research Guide features links to relevant websites and other online resources of particular interest.


Reference works


Leading articles

Periodicals, serial publications, special issues

New titles

1. Zagadnienia prawa traktatów w aktualnych pracach Komisji Prawa Międzynarodowego Organizacji Narodów Zjednoczonych
Zagadnienia prawa traktatów w aktualnych pracach Komisji Prawa Międzynarodowego Organizacji Narodów Zjednoczonych / Anna Szarek-Zwijacz. - Warszawa : Bellona. - Page 109-132 In: Kierunki rozwoju współczesnego prawa międzynarodowego / Karol Karski, ISBN 9788311137165: (2015), Page 109-132. - 2015
Keywords: United Nations, International Law Commission, Law of treaties,

Librarian's choice

  • Djeffal, C., Static and Evolutive Treaty Interpretation: a Functional Reconstruction, Cambridge: Cambridge University Press, 2016.

    How should international treaties be interpreted over time? This book offers fresh insights on this age-old question. The Vienna Convention on the Law of Treaties (VCLT) sets out the rules for interpretation, stipulating that treaties should be interpreted inter alia according to the 'ordinary meaning' of the text. Evolutive interpretation has been considered since the times of Gentili and Grotius, but this is the first book to systematically address what evolutive interpretation looks like in reality. It sets out to address how and under what circumstances it can be said that the interpretation of a treaty evolves, and under what circumstances it remains static. With the VCLT as its point of departure, this study develops a functional reconstruction of the rules of treaty interpretation, and explores and analyses how the International Court of Justice and the European Court of Human Rights have approached the issue.

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  • Törber, G., The Contractual Nature of the Optional Clause, Oxford, Portland, Oregon: Hart Publishing, 2015.


    The International Law Commission’s Guiding Principles for Unilateral Declarations and its Guide to Practice on Reservations to Treaties are among the recent developments in international law. These developments support a new assessment on how optional clauses (eg Art 62(1) of the American Convention on Human Rights) and especially the Optional Clause (Art 36(2) of the Statute of the International Court of Justice (ICJ)) can be characterised and treated. The question is in how far optional clauses and the respective declarations can be considered a multilateral treaty or a bundle of unilateral declarations and to what extent one of the corresponding regimes applies.

    Based on inter alia on the jurisprudence of the Permanent Court of International Justice and the ICJ on the Optional Clause, but also on the relevant jurisprudence of the Inter-American Court of Human Rights and the European Court of Human Rights and the General Comments of the United Nations Human Rights Committee, this book provides a comprehensive assessment of all legal issues regarding the Optional Clause and also optional clauses in general. The book deals with the making of Optional Clause declarations, the interpretation of such declarations and reservations made to the declarations as well as the withdrawal or amendment of declarations.

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  • Oliveira Mazzuoli, V. de, The Law of Treaties: A Comprehensive Study of the 1969 Vienna Convention and Beyond, Rio de Janeiro, Editora Forense, 2016.

    The Law of Treaties

    The extraordinary growth in the number of international treaties concluded in recent decades has made awakening around the world to study the Law of Treaties. In Brazil, in particular, the issue has gained greater prominence only recently, due to the delayed ratification of the Vienna Convention on the Law of Treaties. In fact, since the signing of the Convention on 23 May 1969, more than forty years passed before the final engagement of Brazil to the text of Vienna, which took place only on 25 September 2009. This book - which is the first to be published between us after the Brazilian ratification of the Vienna Convention of 1969 - come fill this large gap in the homeland doctrine. Written by one of the most respected Brazilian internationalist, the book that now reaches the hands of readers versa with depth on all issues related to the theory of treaties, as shown by the detailed summary. Each subject studied in the work deserved harsh treatment, since the precise use of words in the text and the methodological rigor used up the reasons for each point versed with what is best in doctrinal level in the world.

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  • Gardiner, R., Treaty Interpretation, Second Edition, Oxford, United Kingdom, Oxford University Press, 2015.


    This book explains the rules for interpretation of treaties and gives examples of their application in national and international jurisdictions. The rules of treaty interpretation codified in the Vienna Convention on the Law of Treaties now apply to virtually all treaties which may be encountered in an international context and also within national legal systems where treaties have an impact on a large and growing range of matters. The rules of treaty interpretation differ somewhat from typical rules for interpreting legal instruments and legislation within national legal systems. Lawyers, and also some administrators, diplomats, and officials at international organizations, are increasingly likely to encounter issues of treaty interpretation which require not only knowledge of the relevant rules of interpretation, but also how these rules have been, and are to be, applied in practice. Now that the codified rules of treaty interpretation have been in force for some twenty-five years, there is a considerable body of case law on their application. This case law, combined with the history and analysis of the rules of treaty interpretation, provides a basis for understanding this most important task in the application of treaties internationally and within national systems of law.

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  • Merkouris, P., Article 31(3)(c) VCLT and the Principle of Systems Integration: Normative Shadows in Plato's cave, Leiden, Boston, Brill Nijhoff, 2015.


    In Article 31(3)(c) VCLT and the Principle of Systemic Integration: Normative Shadows in Plato’s Cave the author tackles a provision on treaty interpretation that has risen in prominence, Article 31(3)(c) VCLT. This article, which enshrines the principle of systemic integration, and its exact scope has become and continues to be a hotly debated subject in academic and judicial circles.
    Through an examination of both its written and unwritten elements, the author argues that the ‘proximity criterion’ is the optimal way of understanding and utilizing this provision, that conflict resolution principles may be of use within Article 31(3)(c) and finally, that the principle of systemic integration is indispensable not only for interpreting treaty provisions but customary international law as well.

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  • Bianchi, A., D. Peat, M. Windsor (eds.), Interpretation in International Law, Oxford, New York, Oxford University Press, 2015.


    The relevance of interpretation to the academic study and professional practice of international law is self-evident. As new insights on the practice and process of interpretation abound in other disciplines, international law and international lawyers have largely remained wedded to a rule-based approach, focusing almost exclusively on the Vienna Convention on the Law of Treaties. Such an approach neglects interpretation as a distinct and admittedly broader field of theoretical inquiry. Interpretation in International Law brings together established and emerging international legal scholars to interrogate interpretation as a central concept in international law. The edited collection is creatively structured around the metaphor of the game, which captures and illuminates all the constituent elements of an act of interpretation. The object of the game of interpretation is to persuade one's audience that your own interpretation of the law is the correct one. The rules of play are known and complied with by the players, even though which cards to play is left to the skills and strategies of the individual players. There is also a meta-discourse about the game of interpretation 'playing the game of game-playing' which involves reflection about the nature of the game, its underlying stakes, and who gets to decide by what rules one should play. Through a series of diverse contributions, Interpretation in International Law reveals interpretation as an inescapable feature of all areas of international law. It will be of interest and utility to all international lawyers whose work touches upon theoretical or practical aspects of interpretation.

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  • The Peace of Christmas Eve

    Peace is an elusive thing. For many, the attraction of the Christmas season is the momentary fulfillment of that dream, the wonderful moment of ‘Peace on Earth’. For one night, it seems possible. As Christmas approaches, we experience a sense of ‘Peace on Earth’. A few times in history, this sense of peace at Christmas had real impact on human affairs. A little known example is the the signing of the Treaty of Ghent on Christmas Eve, December 24, 1814, ending a war, the War of 1812, between the United States and the British Empire and their allies.

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See also

More Research guides on Public International Law

PPL keywords