The integration paradox: an ILC view on the EU contribution to the codification and development of rules of general international law

The contribution of international organisations (IOs) to the process of identification, codification or development of rules of general international law is one still enveloped in a measure of mystery. While the United Nations (UN) International Law Commission (ILC) has long relied on IOs’ practice, and the practice of States within IOs, in carrying out its work, it has only recently begun to address the role that IOs might play in the formation or expression of rules of customary international law, jus cogens or general principles of law. In this process, the European Union (EU) has long been seen as an ‘odd’ fit. From the point of view of general international law, EU integration forms an apparent paradox: on the one hand, the degree of transfer of powers to the organisation renders it particularly well suited to be a ‘ jus generative’ force and a useful source of practice for the ILC’s work; on the other, its ‘exceptionalism’ often militates against the reliance on EU-related practice as evidence of existing or emerging rules of general application. This article looks at the effects of this ‘integration paradox’ in the ILC’s work by reviewing the references to, and the use of, EU practice in eight distinct codification projects, combined with interviews with ILC members and EU officials. It provides an ILC (outside) view on the relevance of EU practice for the identification, codification, and development of rules of general international law. This view, in turn, has implications for the operation of an EU (inside) foreign policy objective: its ambition to contribute to the development of international law, as expressed in Article 3(5) of the Treaty on European Union (TEU).