In an era marked by geopolitical fragmentation and open challenges to international norms, the relevance of international law is often questioned. Yet it is precisely under such conditions that international law is most significant. To that end, understanding the institutions that interpret and articulate international law—particularly in moments of strain—is essential.
One such institution is the United Nations International Law Commission (ILC), which occupies a unique position in the international legal order. Established in the aftermath of WWII, the Commission was conceived as a technical body within the UN system, composed of international legal experts—acting in their individual capacity—who were tasked with the progressive development and codification of international law. In serving as a forum for reasoned legal debate on the most pressing topics of international law, the ILC has shaped the language, structure, and evolution of international legal doctrines for over seven decades.
This post is the first in a multi-part series connected to my work as an adjunct professor at American University, Washington College of Law, where I am teaching an upper-level practicum on the ILC. In this course, students assist ILC member Claudio Grossman in his work as Special Rapporteur on the Immunity of State Officials from Foreign Criminal Jurisdiction, as well as in his broader work as a member of the Commission. The aim of this series is to make the institutional role, working methods, and legal significance of the ILC more accessible to readers beyond the classroom.
As always, if there’s something you’d like to see added, clarified, or explored further, I’m happy to hear from you!
Theoretical Roots
The roots of the ILC lie in the 19th-century codification movement, which sought to replace the uncertainties of customary international law with written legal instruments. Prior to this period, international law was largely understood as an unwritten body of custom and general principles derived from State practice and scholarly writings. Codification emerged as an effort to systematize and clarify these norms by translating them into authoritative written instruments.
Private learned societies played a crucial role in this early phase. Institutions such as the Institute de Droit International and the International Law Association (both established in 1873) and the Harvard Research in International Law (established in 1927) sought to promote legal certainty through scholarly consensus-building and draft conventions, many of which later informed the work of diplomatic conferences convened by States to adopt multilateral treaties codifying existing international law.
These initiatives reflected a broader belief that codification could enhance predictability, constrain arbitrary State behavior, and strengthen the rule of law at the international level.
Pre-United Nations Codification Efforts
The first major intergovernmental attempts at codification took place at the Hague Peace Conferences of 1899 and 1907. While primarily concerned with the laws of war and dispute settlement, these conferences demonstrated the feasibility (and limits) of multilateral legal regulation. However, plans for a third conference were ultimately derailed by the outbreak of WWI.
More ambitious efforts followed under the auspices of the League of Nations, which initiated the first worldwide attempt to codify entire fields of international law. In 1924, the League’s Assembly established the Committee of Experts for the Progressive Codification of International Law and tasked it with identifying topics “sufficiently ripe” for international regulation. This led to the 1930 Codification Conference, during which delegates from 47 States met in the Hague from 13 March to 12 April 1930. The conference was intended to address 3 of the 5 topics considered “ripe for international agreement” by the Committee of Experts: (1) nationality, (2) territorial waters, and (3) State responsibility for injuries to aliens. However, despite high expectations, the conference only produced international instruments addressing the topic of nationality; conference attendees were unable to adopt any conventions related to the other two topics.
Later, on 25 September 1931, the League of Nations adopted a resolution on the procedure of codification, which mainly addressed strengthening governmental influence in every stage of the codification process—a theme that was later incorporated into the ILC’s Statute. However, beyond this procedural intervention, the League of Nations made no further efforts to contribute to the codification movement.
The San Francisco Conference and the UN Charter Framework
From 25 April to 26 June 1945, representatives from fifty States met in San Francisco, California at the United Nations Conference on International Organization (commonly known as the “San Francisco Conference”). The nations in attendance were those that declared war on Germany and Japan, and had previously subscribed to the United Nations Declaration. Working off the Dumbarton Oaks proposals, the Yalta Agreement, and the amendments proposed by various governments, attendees finalized and adopted the Charter of the United Nations and the Statute of the International Court of Justice.
A central debate during the drafting process concerned the extent of the United Nations’ legislative authority. While States firmly rejected granting the UN legislative authority to enact binding rules or impose general conventions via majority vote, they accepted a more modest (but consequential) role for the General Assembly: the powers of study and recommendation.
Accordingly, UN Charter Article 13(1) grants the General Assembly the power to “initiate studies and make recommendations for the purpose of . . . encouraging the progressive development of international law and its codification.”
Establishment of the International Law Commission
Granting an institution power in a statute is one thing; implementing that power is another. The General Assembly needed to determine how it could fulfill its obligations under Article 13(1). Accordingly, during its first session in 1946, the General Assembly adopted Resolution 94(I) which established the Committee on the Progressive Development of International Law and its Codification (commonly known as the “Committee of Seventeen”), and tasked the Committee with recommending possible procedures through which the General Assembly could fulfill its Article 13(1) obligations.
After thirty meetings, held from 12 May to 17 June 1947, the Committee of Seventeen adopted a report recommending the creation of an international law commission and provided draft provisions that could serve as the basis for such a commission’s statute.
A few months later, in November 1947, the General Assembly adopted the Committee of Seventeen’s recommendations in General Assembly Resolution 174(II) and formally established the ILC. The Commission held its first session on 12 April 1949, marking the beginning of a new institutional approach to international lawmaking—one grounded in expertise, continuity, and methodological rigor rather than ad hoc diplomacy.
Institutional Evolution and Statutory Amendments
Since its adoption in 1947, the ILC’s Statute has been amended six times. These amendments were initiated partly on the initiative of the Commission and partly on that of Governments. The amendments related to both practical and representational concerns, including the size and regional composition of the Commission, the length of members’ terms, the expenses to be paid to the members, and the location of its meetings. These adjustments reflected the changing demographics and political realities of the international community, particularly decolonization and the expansion of UN membership.
The ILC’s Contribution to International Law (1947–Present)
Since its inception, the ILC has addressed the most pressing issues of international law. Its work has directly facilitated the development of international law through its contributions to landmark treaties, including the Vienna Convention on the Law of Treaties, the United Nations Convention on the Law of the Sea, and the Rome Statute of the International Criminal Court. In other instances, such as the Articles on Responsibility of States for Internationally Wrongful Acts (“ARSIWA”, also known as the “Articles on State Responsibility”), the Commission’s outputs have not been converted into treaties but nonetheless exert profound normative influence through widespread citation by courts, tribunals, and States.
Importantly, the ILC’s authority derives not from formal binding force, but from the perceived quality, neutrality, and coherence of its legal reasoning. Its commentaries often play a decisive role in clarifying the content of international law, functioning as a point of reference for both codification and interpretation even when the Commission’s work does not culminate in a treaty. The Commission’s work supplies a common legal vocabulary through which States, courts, and scholars can discuss the content of international legal obligations (or the lack thereof). Without institutions like the ILC, States would still fight—but they would no longer argue in legal terms.
Course Materials
References
- International Law Commission, Website: https://legal.un.org/ilc/ilcintro.shtml; https://legal.un.org/ilc/league.shtml; https://legal.un.org/ilc/drafting.shtml
Additional Reading
- Stephen C. Schlesinger, Act of Creation: The Founding of the United Nations (2003).
- 70 Years of the International Law Commission (United Nations, 2020).
- Seventy Years of the International Law Commission: Drawing a Balance for the Future (United Nations, 2021).
- 75 Years of the International Law Commission (RRU Centre for International Law, 2024).
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