Over the past decades international affairs have been increasingly legalized. International law has dramatically expanded into new fields and taken on new challenges. Despite this development, there has been little in-depth scholarship on what impact these changes have had on the field of international legal theory, how it is taught, and where it is going. This volume investigates the major developments in the field and explores the core assumptions and concepts, analytical tools, and key challenges associated with different approaches. An outstanding team of legal academics provides an accessible overview of competing theoretical movements, and a more in-depth understanding of the strengths, preoccupations, insights, and limits of those schools of thought. The contributions provide an authoritative account of current thinking about the theoretical foundations of contemporary international law and will serve as an indispensable resource for students, scholars, and practitioners.