Lecture summary: Civil war is the greatest military challenge of our time in terms of real time suffering. The mere mention of Afghanistan, Congo, Libya, Somalia, and Syria supports the point. Internal conflicts like these not only result in mass death and destruction of the built and natural environments, they leave populations traumatized for generations. And they impact life far beyond the places of fighting. Mass migration from these wars is helping to trigger demagoguery and destabilization seen around the world. International lawyers are engaged with many of the issues raised by civil war, yet they have done relatively little work on the central questions of whether resort to armed rebellion and intervention in them are lawful. The lecture will investigate the lack of attention to these core questions. It will reveal the long-running, unresolved debate over the morality of resort to civil war. Without a consensus on the moral question, the law remained equivocal. Does that remain true today? Mary Ellen O'Connell is the Robert and Marion Short Professor of Law and Research Professor of International Dispute Resolution—Kroc Institute for International Peace Studies, University of Notre Dame. Professor O’Connell holds a BA in history from Northwestern University, an MSc in International Relations from LSE, an LLB and PhD from the University of Cambridge, and a JD from Columbia University. She has served as a vice president of the American Society of International Law and chaired the Use of Force Committee of the International Law Association. Before Notre Dame, she was a faculty member at The Ohio State University, the Johns Hopkins University Nitze School of Advanced International Studies Bologna Center, and Indiana University. She was a professional military educator for the U.S. Department of Defense in Garmisch-Partenkirchen, Germany and practiced law with the Washington, D.C.-based international law firm, Covington & Burling. She also worked as Sir Elihu Lauterpacht’s research assistant. Useful links: https://www.cambridge.org/core/books/art-of-law-in-the-international-community/15625F4C8A1B44E00774E078910F7CEA https://referenceworks.brillonline.com/entries/the-hague-academy-collected-courses/*-ej.9789004297647.053_312 https://global.oup.com/academic/product/human-rights-and-personal-self-defense-in-international-law-9780190655020?cc=us&lang=en&