‘It is easy to get lost in the maze of optional clause declarations submitted under Article 36(2) of the ICJ Statute. Nearly all States limit the Court’s jurisdiction by supplementing their declarations with reservations, and these become longer and more complex. Robert Kolb’s newest book is a guide through the maze of the optional clause system. It identifies standard types of reservations, highlights trends in the practice of States and distils key takeaways from the ICJ’s jurisprudence. It does not ignore the complexity of the topic, but provides us with a roadmap to confront it. Students, academics and practitioners will read it with benefit.’