Non-state threats and actors have become key topics in contemporary international security as since the end of the Cold War the notion that state is the primary unit of interest in international security has increasingly been challenged. Statistics show that today many more people are killed by ethnic conflicts, HIV/AIDS or the proliferation of small arms than by international war. Moreover, non-state actors, such as non-governmental organizations, private military companies and international regimes, are progressively complementing or even replacing states in the provision of security. Suggesting that such developments can be understood as part of a shift from government to governance in international security, this book examines both how private actors have become one of the main sources of insecurity in the contemporary world and how non-state actors play a growing role in combating these threats.