Codification

In international law, codification refers to the formal restatement of existing customary international law into written, structured instruments — usually multilateral treaties. It is distinguished from progressive development, which involves drafting new rules where state practice is unsettled, although the two processes often overlap in practice.

The United Nations Charter, in Article 13(1)(a), tasks the General Assembly with initiating studies and recommendations to encourage "the progressive development of international law and its codification." To carry out this mandate, the GA created the International Law Commission (ILC) in 1947 (Resolution 174(II)), composed of independent experts elected by the Assembly. The ILC drafts articles, circulates them to states for comment, and forwards finalized texts to the GA, which may convene a diplomatic conference to adopt them as a treaty.

Landmark codification treaties drafted with ILC involvement include:

• The four Geneva Conventions on the Law of the Sea (1958), later largely superseded by UNCLOS (1982).
• The Vienna Convention on Diplomatic Relations (1961).
• The Vienna Convention on Consular Relations (1963).
• The Vienna Convention on the Law of Treaties (1969).
• The Rome Statute of the International Criminal Court (1998), building on ILC work on a draft code of crimes.

Codification serves several functions: it clarifies ambiguous customary rules, makes the law accessible to non-specialist states, reduces disputes over the content of obligations, and creates a written reference point for courts and tribunals. However, codification can also "freeze" customary law at a particular moment, and unratified codification treaties may still influence practice as evidence of opinio juris.

At the domestic level, codification refers to the consolidation of statutes and case law into comprehensive codes — the French Code civil (1804) and the German BGB (1900) being the canonical examples in civil-law systems.