The under-regulation of the private security industry has increasingly become a topic of media and academic interest. This Adelphi Paper enters the debate by explaining why the industry requires further regulation, and what is wrong with the current system. It begins by briefly defining the industry and explaining the need for more effective regulation, before analysing three types of regulation: domestic, international and informal (including self-regulation).

Sarah Percy is a Research Associate in the Oxford Leverhulme Programme on the Changing Character of War. She received a master's and doctorate in international relations from the University of Oxford (Balliol College). She also holds a BA (Hons) in political studies from Queen's University in Canada. Prior to taking up her current post she taught in King's College London's Defence Studies Department at the Joint Services Staff and Command College, where she still lectures on the subject of private force. Her research interests include: mercenaries, private military companies and the privatisation of force; the use of norms to regulate warfare; and the relationship between international law and international relations. More general areas of interest include international security and international relations theory. She is converting her doctoral dissertation, entitled 'Sons of Iniquity: The Origins, Evolution and Influence of a Norm against Mercenary Use', into a book to be published by Oxford University Press in 2007. The thesis received the CAMOS dissertation prize at the American Political Science Association Annual Meeting in August 2006.

Chapter 1 Introduction; Chapter 2 An Overview of the Industry and the Need for Regulation; Chapter 3 Domestic Regulation; Chapter 4 International Regulation; Chapter 5 Informal Regulation; Chapter 6 Conclusion;