The authors of this monograph, members of the Project on Information Technology and International Security at Stanford University's Center for International Security and Arms Control, have surfaced and explored some profound issues that will shape the legal context within which information warfare may be waged and national information power exerted in the coming years. They note that despite the newness of both the technology of Information Warfare (IW) and the evolving concepts for its employment, legal constraints will almost certainly apply to IW. Also noting that concepts of sovereignty based on physical territoriality do not function well in cyberspace, the authors observe that there is no authoritative legal or international agreement as to whether an IW "attack" equals an "attack" or "use of force" in the traditional sense. With this as a context, the authors offer several legal approaches the United States could employ to protect the national information infrastructure or clarify options useful for offense, defense, or retaliation. They are under no illusions that they have answered all of the questions relating to information warfare and international law, but rather can take great satisfaction in having cogently and thoroughly explored key legal questions and issues that information warriors, jurists, and policy makers will wrestle with in the future. In doing so, they have made a significant and lasting contribution to national and international security, stability, and peace.