In this discussion of the impact of the International Law Commission's work, the author focuses on the law in action, as opposed to the law as it is found in the books. He gives particular emphasis to examples from the law of treaties, the law of State responsibility, international humanitarian law and, to highlight the relationships between those engaged in the law, State immunity. The author begins by discussing the relevance of the Commission's work to national law, particularly to the development and codification of national law, and then considers the effect in national and international courts of the work of the Commission. He concludes with suggestions as to how the Commission's role might be enhanced.