Book excerpt: This book provides an interdisciplinary examination of international law by addressing four critical questions: How are international legal rules distinctive? How does an investigator determine the existence of a rule of international law? Does international law really matter in international politics? and What effect could the changing nature of international relations have on international law? Using Constructivist theory, Arend argues that international law can alter the identity of states, and, consequently, have a profound impact on state behavior.