This book offers a comprehensive analysis of the international law applicable to cyber operations, including a systematic examination of attribution, lawfulness and remedies. It demonstrates the importance of countermeasures as a form of remedies and also shows the limits of international law, highlighting its limits in resolving issues related to cyber operations. There are several situations in which international law leaves the victim State of cyber operations helpless. Two main streams of limits are identified. First, in the case of cyber operations conducted by non-state actors on the behalf of a State, new technologies offer various ways to coordinate cyber operations without a high level of organization. Second, the law of State responsibility offers a range of solutions to respond to cyber operations and seek reparation, but it does not provide an answer in every case and it cannot solve the problem related to technical capabilities of the victim.

Winner, 2021 Book Prize, European Society of International Law (ESIL)

'An important and illuminating contribution to a vital but infrequently explored area of 'cyber hostilities'.'

JHH Weiler - Editor-in-Chief, European Journal of International Law

'In line with the Paris Call for trust and security in the cyberspace launched by President Macron, France firmly believes that the application of International Law, including the UN Charter in its entirety, international humanitarian law and customary international law, is and needs to remain the foundation for peace and security in cyberspace. François Delerue’s in-depth analysis constitutes an essential intellectual contribution towards building more trust, security and stability in cyberspace.'

Henri Verdier - Ambassador for digital Affairs, French Ministry for Europe and Foreign Affairs

'François Delerue’s stimulating and thought-provoking study is a must read for those seeking a fresh look on international law and contemporary challenges. It is a valuable contribution to classical international scholarship, while providing readers with technical background necessary to better understand current legal issues in cyberspace. Its particular strength is a detailed yet practical take on attribution, due diligence and state responsibility with poignant references to resilience and cyber operations.'

Joanna Kulesza - University of Lodz, Poland

'Cyber Operations and International Law offers an important - and comprehensive - treatment of international law’s application to State and State-sponsored operations in cyberspace. Taking readers beyond the well-trodden grounds of armed conflicts, Delerue covers a range of international legal issues, including sovereignty, non-intervention, counter-measures, and human rights. In doing so, he provides an accessible account of the technology and its challenges to the efficacy of international law in regulating global cybersecurity.'

Duncan B. Hollis - Temple University, Philadelphia

'In a context of enhanced strategic competition between great powers and proliferation of state sponsored cyber attacks that threaten international peace and cyber stability, François Delerue's Book offers a brilliant and insightful contribution to the debates about how international law applies to cyber operations. His sophisticated and thorough analysis of complex legal debates, supported by well-documented examples, is both accessible to non-lawyers and of great value for scholars and practitioners.'

Frederick Douzet - Université Paris 8, Director of GEODE

‘This study is illustrated by numerous examples drawn from State practice, demonstrating the topicality of the subject and constituting thus a useful manual for professionals [of] law. The author succeeds, while leading [an] in-depth analysis of the subject, to [make] accessible to legal and non-legal readers the 'old concepts of international law' which for some seem to find a second youth in the era of the multiplication of cyber operations.’

Aude Géry Source: Hérodote

‘Cyber Operations and International Law is a compelling, logical, and important book that touches on all of the critical international law topics while asking difficult questions … François Delerue successfully accomplishes the heroic task of untangling both the technology and law surrounding cyber operations in a book that will undoubtedly serve as a leading foundation for further scholarly activity in this space.’

Ido Kilovaty Source: American Journal of International Law

‘The analysis is particularly useful as there are few generalist works in international law on cybersecurity. Delerue's work offers another doctrinal approach, for a useful comparison of scientific analyzes.’

Anne-Thida Norodom Source: Politique étrangère

‘The book by François Delerue provides an analysis of the strengths and weaknesses of a legal order facing unprecedented challenges-from cyber attackson nuclearplants to election meddling through digital espionage. The result of Delerue 's analysis is a comprehensive study of the currentstate of IL applicable to cyber operations;in its length, depth, and thor-oughness one of the first of its kind. Taking the classic law of state responsibility as his startingpoint and foundation,the author meticulously lays out the international legal framework limiting states' behavior in cyberspace. The book will not only appeal to international legal scholars however. Delerue makes an effort to bridge the gap between lawyers,computer- and political scientists, explaining the essentials of each discipline to the others where necessary.’

Rachel F. Behring Source: Heidelberg Journal of International Law

'Delerue is a research fellow in cyber defense and international law at the Institute for Strategic Research … and his deep knowledge of cyber security and cyber defense and their relationship with international law is evident in the book. Delerue cogently explains difficult technical concepts in the field of cyber operations and makes these notions easily comprehensible for international lawyers. The book has many examples from real life cases of wrongful cyber operations and these examples ensure that the author’s reasoning becomes more relatable … the book is an excellent academic endeavour.’

Upasana Dasgupta Source: Asian Journal of International Law

‘The author has articulated technical and legal issues in such a way that a pure legal mind will also grasp the technical part and be able to relate with legal norms and principles. … The uniqueness of the book is vivid … For future disputes relating to state responsibility for cyber operations, this book will surely be a guiding text, because articulated case studies and hypothetical examples will guide to draw arguments.’

Mostafa Hosain Source: Bangladesh Journal of Law