Codification of International Law: The ILC and the UN

Customary international law can be uncertain, and the absence of a legislature makes it slow to adapt. Codification sets existing rules down in written form, and progressive development creates new rules where practice is thin. The UN Charter gives this task to the General Assembly, which carries it out mainly through the International Law Commission. This note covers the mandate, the Commission, its work and the wider codification effort.

1. The Mandate

• Article 13(1)(a), UN Charter. The General Assembly shall initiate studies and make recommendations for the purpose of encouraging the progressive development of international law and its codification.
• Codification. Under Article 15 of the ILC Statute, the more precise formulation and systematisation of rules of international law in fields where there already has been extensive state practice, precedent and doctrine.
• Progressive development. The preparation of draft conventions on subjects not yet regulated by international law, or in which the law has not yet been sufficiently developed in state practice.
• In practice. The two are hard to separate; most texts combine statements of existing law with new rules.

2. The International Law Commission

• Establishment. Created by the General Assembly by resolution 174 (II) of 1947; it meets annually in Geneva.
• Composition. 34 members since 1981, persons of recognised competence in international law elected by the General Assembly for five year terms, serving in their individual capacity and representing the main forms of civilisation and principal legal systems.
• Relationship with the Assembly. The Commission reports each year to the Sixth (Legal) Committee of the General Assembly, where states comment on its work.
• Indian members. India has been represented on the Commission, including by Radhabinod Pal and P.S. Rao, who served as Special Rapporteur on prevention of transboundary harm.

Figure 1: How the Commission works

3. What the Commission Has Produced

Figure 2: Major outputs of the Commission

• Treaties based on its drafts. The four Geneva Conventions on the Law of the Sea, 1958; the Vienna Conventions on Diplomatic Relations, 1961, Consular Relations, 1963, and the Law of Treaties, 1969; the conventions on succession of states, 1978 and 1983; the Vienna Convention on treaties of international organisations, 1986; the Watercourses Convention, 1997; and the Convention on Jurisdictional Immunities of States, 2004, not yet in force.
• The International Criminal Court. The Commission's 1994 draft statute was the basis for negotiations that led to the Rome Statute, 1998.
• Articles and conclusions. The Articles on Responsibility of States for Internationally Wrongful Acts, 2001, of which the General Assembly took note, are widely applied by courts; other texts include diplomatic protection (2006), identification of customary international law (2018) and peremptory norms (2022)
• Crimes against humanity. The Commission adopted draft articles in 2019; by resolution 79/122 of 4 December 2024, the General Assembly decided to convene a conference of plenipotentiaries, meeting in 2028 and 2029, to negotiate a convention.

4. Other Codification Efforts

• Before the UN. The Hague Conferences of 1899 and 1907 codified the laws of war; the League of Nations' Hague Codification Conference of 1930 covered nationality, territorial waters and state responsibility but produced agreement only on nationality.
• Private bodies. The Institut de Droit International and the International Law Association, both founded in 1873, and the Harvard Research in International Law (1927 to 1939)
• UNCITRAL. The UN Commission on International Trade Law, established in 1966, harmonises trade law through conventions and model laws.
• AALCO. The Asian-African Legal Consultative Organization, set up in 1956 with its secretariat in New Delhi, advises member states on matters before the Commission.
• Human rights and specialised bodies. Many treaties are drafted outside the Commission, such as human rights conventions within the UN human rights machinery and UNCLOS, 1982 at the Third UN Conference on the Law of the Sea.

5. Merits and Limits

• Merits. Greater certainty, participation of new states in shaping the law, and authoritative texts that courts can apply.
• Limits. Conventions bind only parties and may attract few ratifications; codification can freeze rules and reopen settled questions; drafting is slow.
• Influence without ratification. Texts not adopted as treaties, such as the 2001 Articles, still carry weight as statements of custom.

6. Frequently Asked Questions

What is the difference between codification and progressive development?

Codification puts into precise written form rules already settled by extensive practice and precedent. Progressive development drafts rules on subjects that the law does not yet regulate or regulates insufficiently.

Are the ILC Articles on State Responsibility a treaty?

No. The General Assembly took note of them in 2001 without adopting a convention, but courts and tribunals treat many of them as reflecting customary international law.

How many members does the International Law Commission have?

Thirty four since 1981. They are elected by the General Assembly for five year terms and serve in their individual capacity, not as representatives of their governments.

Did the ILC draft the UN Convention on the Law of the Sea, 1982?

No. The Commission's drafts led to the four Geneva Conventions of 1958, but UNCLOS was negotiated directly by states at the Third UN Conference on the Law of the Sea from 1973 to 1982.

7. Related Topics

• Topic 7: Sources of International Law. Article 38 and its gaps.
• Topic 13: Law of Treaties I. The Vienna Convention, 1969.
• Topic 56: United Nations. The General Assembly and its committees.