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

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  • Kolb, R., The Law of Treaties: an Introduction, Cheltenham, UK : Northampton, MA, USA, Edward Elgar Publishing, 2016.


    Permeating all facets of public international law, the modern law of treaties is a fundamental aspect of governance in the ‘democratized’ world. In this contemporary introduction, Robert Kolb provides a refreshing study that is both legally analytical and practical. Written in a highly readable style, the book explores the key topics through concise chapters, which are organized into two parts. The first of these gives a structured overview of the law of treaties along with practical examples. The second provides a critical engagement with the underlying issues and discusses the multi-dimensional problems raised by legal regulations, explored through specific case studies.

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  • DiStefano, G., G.Gaggioli et A.Hêche, La Convention de Vienne de 1978 Sur la Succession d'États en Matière de Traités: Commentaire Article par Article et Etudes Thématiques, Bruxelles, Bruylant, 2016.


    La Convention de Vienne de 1978 traite d’un problème intemporel dans la vie internationale des États, à savoir leurs mutations territoriales. Il s’agit là d’une réalité internationale qui survit au phénomène de la décolonisation, mutation territoriale hautement typée et délimitée historiquement. Les exemples sont innombrables. L’on peut mentionner la réunification de l’Allemagne, l’éclatement de l’Union soviétique, le démembrement de la Yougoslavie, la séparation entre la Tchéquie et la Slovaquie, la sécession de l’Erythrée de l’Ethiopie, la séparation du Timor oriental de l’Indonésie, la sécession du Pakistan oriental (Bangladesh) du Pakistan. La pratique récente, relative au Kosovo notamment, qui a déclaré son indépendance le 17 février 2008, met en exergue l’actualité juridique du sujet. Des cas de succession d’États dans un futur proche ou lointain ne sont donc pas à exclure. Les régions sécessionnistes et les pulsions séparatistes sont nombreuses, même si très généralement non reconnues par la communauté internationale. Pourtant, la succession d’États n’est toujours pas dotée d’un régime juridique cohérent complet. Il convient dès lors de s’intéresser à cette lacune juridique en partant du traité-clef en la matière qu’est la Convention de 1978. Un commentaire exhaustif, article par article, de cette Convention se révèle donc être nécessaire. Cet ouvrage contient une analyse serrée des apports et des lacunes de cette Convention à la lumière des travaux préparatoires ainsi que de la pratique récente. Il permet ainsi d’identifier les éléments de codification de la Convention de Vienne de 1978, mais aussi de voir en quoi celle-ci a pu donner naissance à des principes et règles coutumières en la matière. Il a pour ambition de remettre au goût du jour cette Convention et d’offrir aux chercheurs intéressés, mais également aux États et sujets concernés et à la communauté internationale une vue d’ensemble détaillée, analytique et systématique du droit actuel en matière de succession d’États et de découvrir ainsi les éléments de continuité et de rupture qui la caractérisent.

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  • 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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  • Wake up call for Europe

    Last Thursday, June 23, the British people voted to leave the European Union in an unprecedented referendum about membership of the European Union. According to the official result 51.9% of the registered voters choose to leave against 48.1% who wanted the United Kingdom to remain a member of the European Union. This blog will assess certain aspects of the outcome of the referendum and will try to clarify what the next steps of the so-called Brexit are.

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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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