Paul F. Diehl and Charlotte Ku's new framework for international law divides it into operating and normative systems. The authors provide a theory of how these two systems interact, which explains how changes in one system precipitate changes and create capacity in the other. A punctuated equilibrium theory of system evolution, drawn from studies of biology and public policy studies, provides the basis for delineating the conditions for change and helps explain a pattern of international legal change that is often infrequent and sub-optimal, but still influential.

"Diehl and Ku's book, particularly its focus on the normative and operating systems, contributes nicely to this growing literature on international legal change." Jacob Katz CoganUniversity of Cincinnati College of Law

Paul F. Diehl is Henning Larsen Professor of Political Science and University Distinguished Teacher/Scholar at the University of Illinois at Urbana-Champaign. He also serves as Director of the Correlates of War Project, the largest data-collection effort on international conflict in the world. His areas of expertise include the causes of war, UN peacekeeping, and international law. Charlotte Ku is Assistant Dean for Graduate and International Legal Studies at the University of Illinois College of Law, and Co-Director of the Center on Law and Globalization, a partnership of the American Bar Foundation and the University of Illinois College of Law. She has written and lectured widely about international law and global governance, international organisations and the teaching of international law.