'… a great strength of the book is that it provides a detailed restatement of the law on self-defence and the crucial issues surrounding it … Ruys' work demonstrates a large amount of research into the content of the customary law, using both an 'incident analysis' approach and a consideration of practice in abstracto (for example, in relation to debates over various UN declarations). This research into state practice is of notable breadth and depth, and forms the cornerstone on which all the book's analysis is built … this is an excellent book on armed attack …' James A. Green, Journal of Conflict and Security Law