The third edition of Ingrid Detter's authoritative work explores the changing legal context of modern warfare in light of events over the last decade. The new edition covers post 9/11 events and the resulting changes in the ethos of war. It analyses the role of military companies sometimes authorised by States to act in war-like situations and examines what their legitimacy means for international society. The edition also discusses certain ‘intrinsic’ rules such as rules giving individuals the right to be spared genocide, torture, slavery and apartheid and assure them basic democratic rights.