For decades, Martti Koskenniemi has not just been an influential writer in international law; his work has caused a significant shift in the direction of the field. This book engages with some of the core questions that have animated Koskenniemi's scholarship so far. Its chapters attest to the breadth and depth of Koskenniemi's oeuvre and the different ways in which he has explored these questions. Koskenniemi's work is applied to a wide range of functional areas in international law and discussed in relation to an even broader range of theoretical perspectives, including history, political theory, sociology and international relations theory. These invaluable insights have been expertly brought together by the volume editors, who identify the key and common themes of many of the book's contributions. This volume demonstrates the importance of critical legal scholarship in the ways international law is enacted, shaped and reshaped over time.