This book explores the human rights consequences of the new mercenarism, as channeled through so-called private military and security companies (PMSCs), and offers an overview of the evolution and status quo of both non-legal (soft law and self-regulation) and legal initiatives seeking to limit them. It addresses various topics, including the impact of the presence of non-state actors on human security using the cases of Afghanistan and Syria; research on PMSCs’ impact on human rights in specific cases; the insufficiency and ineffectiveness of existing direct and indirect legal prohibitions on the use of mercenaries; various aspects of international human rights law and international humanitarian law related to the conduct of PMSCs; soft-law and self-regulation mechanisms; and the international minimum standard in general international law regarding the privatization, export, import, and contracting of PMSCs.