In this paper, Michael Schmitt explores the legality of the attacks against Al Qaeda and the Taliban under the "jus ad bellum," that component of international law that governs when a State may resort to force as an instrument of national policy. Although States have conducted military counterterrorist operations in the past, the scale and scope of Operation Enduring Freedom may signal a sea change in strategies to defend against terrorism. This paper explores the normative limit on counterterrorist operations. Specifically, under what circumstances can a victim State react forcibly to an act of terrorism? Against whom? When? With what degree of severity? And for how long? The author contends that the attacks against Al Qaeda were legitimate exercises of the rights of individual and collective defense. They were necessary and proportional, and once the Taliban refused to comply with U.S. and United Nations demands to turn over the terrorists located in Afghanistan, it was legally appropriate for coalition forces to enter the country for the purpose of ending the ongoing Al Qaeda terrorist campaign. However, the attacks on the Taliban were less well grounded in traditional understandings of international law. Although the Taliban were clearly in violation of their legal obligation not to allow their territory to be used as a terrorist sanctuary, the author suggests that the degree and nature of the relationship between the Taliban and Al Qaeda may not have been such that the September 11 attacks could be attributed to the Taliban, thereby disallowing strikes against them in self-defense under traditional understandings of international law. Were the attacks, therefore, illegal? Not necessarily. Over the past half-century the international community's understanding of the international law governing the use of force by States has been continuously evolving. The author presents criteria likely to drive future assessments of the legality of counterterrorist operatio7.

An exploration of the relationship between different branches of international law and their applicability to terrorism.

The Use of Force and International Law offers an authoritative overview of international law governing the resort to force. Looking through the prism of the contemporary challenges that this area of international law faces, including technology, sovereignty, actors, compliance and enforcement, this book addresses key aspects of international law in this area: the general breadth and scope of the prohibition of force, what is meant by 'force', the use of force through the UN and regional organisations, the use of force in peacekeeping operations, the right of self-defence and the customary limitations upon this right, forcible intervention in civil conflicts, the controversial doctrine of humanitarian intervention. Suitable for advanced undergraduate and postgraduate students, academics and practitioners, The Use of Force and International Law offers a contemporary, comprehensive and accessible treatment of the subject.

Winner of the 2020 ASIL Lieber prize! In Peremptory Norms of International Law and Terrorism (Jus Cogens) and the Prohibition of Terrorism, Aniel de Beer analyses the role of these norms (jus cogens norms) in the fight against terrorism. Jus cogens norms protect fundamental values of the international community, are hierarchically superior and non-derogable. The author argues, based on an analysis of the sources of international law, that the prohibition of terrorism has become the jus cogens norm of our time. She further considers the impact of the status of the prohibition of terrorism as a jus cogens norm on other norms of international law relevant in the fight against terrorism, namely the prohibition of torture, the right to a fair trial and the prohibition of the inter-state use of force.

This is the first book to explore the concept of 'Grotian Moments'. Named for Hugo Grotius, whose masterpiece De jure belli ac pacis helped marshal in the modern system of international law, Grotian Moments are transformative developments that generate the unique conditions for accelerated formation of customary international law. In periods of fundamental change, whether by technological advances, the commission of new forms of crimes against humanity, or the development of new means of warfare or terrorism, customary international law may form much more rapidly and with less state practice than is normally the case to keep up with the pace of developments. The book examines the historic underpinnings of the Grotian Moment concept, provides a theoretical framework for testing its existence and application, and analyzes six case studies of potential Grotian Moments: Nuremberg, the continental shelf, space law, the Yugoslavia Tribunal's Tadic decision, the 1999 NATO intervention in Serbia and the 9/11 terrorist attacks.

The book examines the military and law enforcement responses to international terrorism. Subjects include the legal authority to use military force; determining when the law of armed conflict comes into force; the law of targeting and how this authority is applied to terrorist operatives; preventive detention; prosecution of terrorists by military commission; the legal framework for gathering counter-terrorism intelligence information; prosecuting terrorists and their sponsors; freezing terrorist assets; and civil liability for personal injury or death caused by acts of international terrorism.

This book examines the attempts by the international community and the United Nations to define and criminalise terrorism. In doing so, it explores the difficult legal, ethical and philosophical questions involved in deciding when political violence is, or is not, permissible.