International Law Private Military and Security Companies
Joop Voetelink
  • LAST REVIEWED: 25 September 2019
  • LAST MODIFIED: 25 September 2019
  • DOI: 10.1093/obo/9780199796953-0190


When state armed forces are deployed in the context of armed conflict situations or crisis management operations it has become fairly common that they are accompanied and supported by employees of private business entities, often referred to as Private Military and Security Companies (PMSCs). The name notwithstanding, PMSCs do not have a military status, but are private businesses contracted to perform a wide array of functions that traditionally were carried out by active duty military. These functions include training; logistic support, such as transport, maintenance and repair; base support; and even operational duties, such as collecting and analyzing intelligence and providing armed security services. Although civilians accompanying the armed forces are not a new phenomenon, reliance on the private sector to support military operations has steadily increased since the end of the Cold War. The presence of so many civilians in the area of military operations, working closely together with the military without actually being part of the armed forces, has led to incidents raising a number of legal concerns that have received wide academic attention. Notwithstanding these questions, the private sector has a critical role to play in supporting contemporary military operations. The military’s reliance on this sector is, therefore, today’s reality and is not expected to change in the near future. In early modern Europe it was common practice for territorial entities to strengthen their armies by hiring often foreign fighters in times of tension. With the rise of the nation-state the role of hired forces had gradually diminished and at the start of the 19th century states almost fully relied on national armed forces. In that same period international law further developed focusing on the nation-state as the principal subject of international law. Because involvement of civilians with the armed forces in conflict situations was negligible then, there was no need to regulate in great detail the status of civilians supporting and accompanying armed forces in times of conflict. When the phenomenon of hired fighters reemerged in the post–World War II decolonization period in Africa, efforts were made to fill the gap by addressing the use and conduct of these ‘Mercenaries.’ This process resulted in rather specific rules, which were ill suited to address the consequences of the unexpected rise some decades later of business entities providing military services. While in the literature of the late 1990s and early 2000s attention was first focused on this perceived legal gap, more recent work analyzes the applicability of the existing international legal framework and explores new initiatives to regulate the private sector. The focus of this article is on the latter.

General Overviews

Over the past two decades the topic of PMSCs has been the subject of much scholarly attention from a variety of research traditions (e.g. Jäger and Kümmel 2007 and Singer 2008) and international relations (e.g., Anders 2017) and has also resulted in a number articles and books providing a general overview of legal aspects concerning the use and conduct of these private actors. McDonald 2007 provides an overview of some of the most important legal topics focusing on the use of PMSCs by the United States in Iraq. Francioni and Ronzitti 2011 explores whether international human rights law and international humanitarian law can fill possible accountability gaps. Calazans 2016 offers a concise overview of the three main strands of legal research concerning the use of PMSCs: the status and rights and obligations of these firms and their personnel under international humanitarian law; responsibility of States for PMSC activities; and Regulation of the phenomenon. The same topics are addressed in Moyakine 2015 in a more elaborate way with an emphasis on the responsibility of states for misconduct of PMSC. It must be noted that most legal publications on PMSCs one way or another touch upon these aspects.

  • Anders, Birthe. “Private Military and Security Companies (PMSCs).” Oxford Bibliographies in International Relations, 24 May 2017.

    DOI: 10.1093/OBO/9780199743292-0209

    Regards PMSC research as a subfield of security studies that draws on a variety of disciplines, including law. The main focus of research from an international relations perspective concerns the relation between PMSCs and the state, law and Regulation, contracting in Iraq and Afghanistan, the role of the individual PMSC employees, and contracting of PMSCs by non-state entities.

  • Calazans, Erika. Private Military and Security Companies: The Implications Under International Law of Doing Business in War. Cambridge, UK: Cambridge Scholars Publishing, 2016.

    Concise overview addressing the status of PMSC employees under international humanitarian law, the International Responsibility of states and others, and the regulation of PMSC activities. The book concludes that although PMSCs do not operate in a legal vacuum, accountability for breaches of international law should be enhanced by further developing regulation of PMSC activities.

  • Francioni, Francesco, and Natalino Ronzitti, eds. War by Contract: Human Rights, Humanitarian Law, and Private Contractors. Oxford: Oxford University Press, 2011.

    This edited volume is a result of the EU-funded research project “Regulating the Privatization of ‘WAR’: The Role of the EU in Assuring Compliance with International Humanitarian Law and Human Rights” (From Research to Policy: The PRIV-WAR Project). It explores the question whether existing international human rights law and international humanitarian law can ensure accountability of PMSCs in case of misconduct. In addition, the book examines the international responsibility of states and civil and criminal liability of PMSC personnel.

  • Jäger, Thomas, and Gerhard Kümmel, eds. Private Military and Security Companies: Chances, Problems, Pitfalls, and Prospects. Wiesbaden. Germany: VS Verlag für Sozialwissenschaften, 2007.

    This very broad edited volume takes a multidisciplinary approach looking at the use of PMSCs from different angles, including law. It analyzes the history and development of PMSCs, offers a number of case studies, and explores problems and prospects. The final part of the book focuses on legal issues including regulation of PMSCs.

  • McDonald, Avril. “Ghosts in the Machine: Some Legal Issues Concerning US Military Contractors in Iraq.” In International Law and Armed Conflict: Exploring the Faultlines. Edited by Michael Schmitt and Jelena Pejic, 357–401. Leiden, The Netherlands: Nijhoff, 2007.

    DOI: 10.1163/ej.9789004154285.i-590.75

    The chapter focuses on the use of contractors by the US military in Iraq, providing an overview of some of the most important legal topics, including the status of contractors under international humanitarian law, criminal and civil liability of contractors, and the responsibility of states under international law.

  • Moyakine, Evgeni. The Privatized Art of War: Private Military and Security Companies and State Responsibility for their Unlawful Conduct in Conflict Areas. Cambridge, UK: Intersentia, 2015.

    DOI: 10.1017/9781780685632

    This well-researched book examines the international responsibility of states for conduct of PMSCs and their employees and analyzes the applicability of positive obligations of states under international law. The author proposes that hiring states, as well as states where the PMSCs are operating or where they are registered, can be responsible under international law.

  • Singer, Peter Warren. Corporate Warriors: The Rise of the Privatized Military Industry. Ithaca, NY: Cornell University Press, 2008.

    Classic, multidisciplinary study of PMSCs first published in 2003 and updated in 2008 with a postscript on The Lessons of Iraq (pp. 243–260). The book distinguishes between three basic type of companies according to their location in the battle space: military provider firms, military consultant firms, and military support firms.

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