Helfer & Meyer: The Evolution of Codification: A Principal-Agent Theory of the International Law Commission’s Influence

Laurence R. Helfer (Duke Univ. - Law) & Timothy Meyer (Univ. of Georgia - Law) have posted The Evolution of Codification: A Principal-Agent Theory of the International Law Commission’s Influence (in Custom's Future: International Law in a Changing World, Curtis Bradley ed., forthcoming). Here's the abstract:

The International Law Commission has a mandate from the U.N. General Assembly to codify and progressively develop international law. For most of the ILC’s history, the lion’s share of its work took the form of draft articles adopted by the General Assembly as the basis for multilateral conventions. The ILC’s activities received their principal legal effect during this period through the United Nations treaty-making process, rather than directly on the basis of the ILC’s analysis of what customary international law does or should require. In recent decades, however, the ILC has turned to other outputs — such as principles, conclusions and draft articles that it does not recommend be turned into treaties. Significantly, the Commission often claims that these outputs reflect customary international law.

In this chapter, we argue that increasing political gridlock in the General Assembly has led the Commission to modify the form of the work products it produces. We make three specific contributions to the literature. First, using principal-agent theory we argue that the ILC chooses the work product that maximizes its influence in shaping the evolution of custom. Our core claim is that, as gridlock has limited the General Assembly’s ability either to adopt treaties or decisively reject non-treaty outputs, the Commission has had both the incentive and the discretion to choose other outputs that do not require General Assembly approval.

Second, we provide empirical support for this claim. Drawing upon a new data set that codes all ILC outputs since 1947, we show that the Commission began to favor non-treaty outputs beginning in the early 1990s. This followed a decade when ILC treaty recommendations were not adopted by the UNGA or, if adopted, did not garner sufficient ratifications for the treaties to enter into force.

Third, we argue that the shift away from draft treaties increases the salience of the methodology that the ILC uses to prepare non-treaty outputs. Methodology functions as a de facto substitute for the political blessing that flows from the General Assembly’s adoption of draft treaty articles. Adherence to methodology increases the likelihood that a wider audience — government officials, international judges, national courts and non-state actors — will accept the ILC’s non-treaty work products as valid statements of custom. We thus expect the Commission to select a methodological approach that it expects will be supported by the audience(s) it hopes to persuade.