In This Article Expand or collapse the "in this article" section Codification

  • Introduction
  • Textbooks
  • Judicial Decisions
  • Definition of Codification
  • Codification, Legislation, and Progressive Development
  • Advantages and Disadvantages of Codification
  • Codification Efforts and Methodology
  • Private Codification Efforts

International Law Codification
Annemarieke Vermeer-Künzli
  • LAST REVIEWED: 17 February 2021
  • LAST MODIFIED: 27 March 2014
  • DOI: 10.1093/obo/9780199796953-0079


Codification is the process through which rules of law are committed to written form. It is usually mentioned in one breath with progressive development. Within the broader topic of the sources of international law, codification holds a peculiar place. The process of codification tends to change the law, because transforming unwritten rules into written rules requires precision, systematization, and definition of the relevant terms and rules. These changes can be minor or substantial. As all authors agree, “pure” codification does not exist; it always involves some measure of change. When this change is substantial, it is often is called “progressive development” or “legislation.” History knows both epic failures and celebrated successes. The former includes the 1930 Hague Conference and some of the projects of the International Law Commission (ILC). The latter includes the Vienna Convention on the Law of Treaties and the Vienna Conventions on Diplomatic and Consular Relations. Codification is often seen as beneficial, increasing certainty through the rule of law and the development, coherence, and sophistication of international law. Yet, it is also criticized for decreasing flexibility, creating discord, and creating uncertainty through the vagueness and generality of provisions in codification treaties due to the requirement of consensus. Most post-1945 writings on codification also discuss, analyze, and criticize the work of the ILC, undoubtedly the most influential codifier since its creation. A final word is due on the sources on codification. The topic of codification is somewhat esoteric; only one monograph is dedicated to the topic. The vast majority of papers and chapters discussing codification are part of a Festschrift, Liber Amicorum, Essays in Honour of . . ., or other celebratory works. These often present a somewhat loose discussion on the topic based on the personal views and experience of eminent scholars of international law and former members of the ILC. They often do not present an in-depth, well-researched analysis of the issue proper with an analytical approach evaluating the definition, role, and purpose of codification in international law. These may be interesting and valuable for the insights they give but may also offer repetitive descriptions of received views because the authors had to write something for their friend and colleague. It means that the doctrinal conceptual development is difficult to trace; skepticism about the possibility and purpose of codification was voiced from 1926 onward as were calls for further codification of particular areas or international law, with equal passion and conviction.

General Overviews

For quick overviews of codification, the best is Villiger 1985, offering a comprehensive and thorough introduction, including discussion of most other influential authors. Watts 2006 (cited under Data Sources) is less balanced but includes an extensive bibliography. For thorough overviews, the uncontested point of departure is de Visscher 1926. It is the first comprehensive presentation of the subject that already includes most of the relevant discussions, even though the understanding of codification and its advantages and disadvantages have been further explored and refined in later writings, and although it predates the codification efforts of the United Nations. It expresses the frequently heard idea that more and more precise law will contribute to peace but concludes that the establishment in writing of the fundamental rules of international law is fiendishly difficult. Lauterpacht 1955 is essential reading for understanding the support for codification. Ago 1968 should also be read in this context. This view has been qualified by Aust 2009 (cited under State Responsibility), Vermeer-Künzli (cited under Law of Treaties) and Matz-Lück 2009 (cited under Environmental Law) and others and was strongly criticized in Stone 1957 (cited under Advantages and Disadvantages of Codification), a must-read which is particularly critical of the view that codification offers clarification. Stone concluded that “the time has passed when we can regard programs for the codification of international law as self-evidently praiseworthy and worthy of political and juristic support” (Stone 1957, p. 20). This point has been examined, and criticized, in the only monograph dedicated to the topic (Dhokalia 1970). Another general overview is presented in the report of a colloquy on codification of the French Society for International Law (Société Française pour le Droit International 1999), essays followed by reports of ensuing debates; perhaps not very critical or controversial, it offers a general, if somewhat French, perspective. Thirlway 1972 offers a general introduction to codification in the context of the sources of international law, in particular, customary international law. A more modern, and rather enlightening, overview of codification, including the work of the ILC and other recent efforts is Boyle and Chinkin 2007. It is comprehensive in discussing institutional, state-led, and private codification efforts and is critical in evaluating the results of these and comparing their relative merits. In addition, it discusses selective areas of codification, again with a critical attitude to the work of the various actors involved.

  • Ago, Roberto. “La codification du droit international et les problèmes de sa réalisation.” In Receuil d’études de droit international en hommage à Paul Guggenheim. Edited by Maurice Battelli, et al., 93–131. Geneva, Switzerland: Imprimérie de la Tribune de Genève, 1968.

    Analyzes the problem of codification from the perspective of decolonization, resulting in both the urgent need for more law and the increasing difficulties in obtaining consent on the content of the law.

  • Boyle, A., and C. Chinkin. The Making of International Law. Foundations of Public International Law. Oxford: Oxford University Press, 2007.

    Offers an enlightening overview, including the work of the ILC and other recent efforts. It is comprehensive, discussing both institutional, state-led, and private codification efforts, as well as critical, evaluating the results and comparing the relative merits of those efforts. Also critically discusses selective areas of codification and contributions of the various actors involved. See pp. 163–209.

  • de Visscher, Charles. “La codification du droit international.” Recueil des Cours 6 (1926): 325–472.

    Comprehensive account on the nature, complexities, methods, pros and cons, history, and purpose of codification. Published in 1926, it contains all elements of modern discussion on codification. Concludes that only codification of technical subjects is possible, not the fundamental rules and principles of the law of nations.

  • Dhokalia, R. P. The Codification of Public International Law. Manchester, UK: Manchester University Press, 1970.

    After discussing the historical, conceptual, and ideological background of codification, this book continues to discuss the various efforts of codification, both private and institutional, culminating in an assessment of the work of the ILC. Ends with suggestions for improving the process of codification.

  • Lauterpacht, Hersch. “Codification and Development of International Law.” American Journal of International Law 49 (1955): 16–43.

    DOI: 10.2307/2194097

    Perhaps somewhat idealistic, but this paper presents a very thoughtful and engaged overview of the process of codification—its function, purpose, preferred methodology, advantages, and disadvantages—and the role of the ILC, private parties, and states in this process. Includes the argument in favor of codification.

  • Société Française pour le Droit International. La codification du droit international: Colloque d’Aix-en-Provence. Proceedings of the 32nd Conference of the French Society for International Law, held at the University of Law, Economics and Science of Aix-Marseille, 1–3 October 1998. Paris: Editions A. Pedone, 1999.

    A collection of essays and reports of debates of primarily French scholarship on codifications. Individual chapters discuss the purpose of codification and various perspectives on codification (see the section on Advantages and Disadvantages of Codification) and the methods of codification (see the section on Codification Efforts and Methodology).

  • Thirlway, Hugh. International Customary Law and Codification. Leiden, The Netherlands: Sijthoff, 1972.

    Supporting the increase of written law, this book addresses the general issues of codification through the prism of its relation to custom. In passing, it offers some discussion on what codification is (see the section on Definition of Codification) and its purpose. See, in particular, Chapters 1–5, pp. 1–79.

  • Villiger, Mark. “The Factual Framework: Codification in Past and Present.” In Customary International Law and Treaties. By Mark Villiger, 63–113. Dordrecht, The Netherlands: Martinus Nijhoff, 1985.

    Offering a rather complete, even if descriptive, well-organized, well-structured, and easily accessible overview of codification ranging from the 18th Century British philosopher Jeremy Bentham to the ILC with special emphasis on the law of treaties. Includes a debate on what codification is (expression of existing law and/or development). It is the best place to start for understanding codification.

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