The objective of this dissertation is to understand how the legitimacy of the state’s international use of PMSCs is evolving in contemporary international society. The first part of the dissertation develops an analytical framework that combines theoretical propositions of the English School and the ‘German’ constructivist strand with a reflective-analyticist philosophical ontology and with content and discourse analytical methods. The empirical part of the dissertation provides an overview of contemporary state practice, investigates how international society has responded to state practice in the UN Security Council and UN General Assembly, and finally analyses the roles of members of world society in creating and shaping this discourse.

The empirical analysis points to two major driving forces behind the increased legitimation of the practice. First, the recursive relationship between behaviour and norms means that widespread use of PMSCs reinforces legitimacy. Second, normative shifts in international society have contributed to the legitimation of the practice. On the one hand, norms that are in tension with an expanded PMSC use have become weaker or sidelined, if still strongly supported by some actors: this is the anti-mercenary norm, and particular understandings of self-determination and the monopoly on the legitimate use of force. On the other hand, and partly linked to the weakening of the latter norms, human rights have gained strength as legitimacy principles. In the contestation over the state use of PMSCs, conflicting moves toward legitimation and delegitimation do not cancel each other out. Rather, structural and more immediate factors put strategic efforts and inadvertent moves of legitimation at an advantage while at the same time marginalizing calls for a reduction or prohibition of the state practice. I examine not only how human rights contribute to the legitimation of the practice, but also why and how actors that seek to limit, contain, or reverse the state practice have increasingly lost ground.

Overall, the dissertation contributes to empirical research by substantiating claims of an increased legitimation of PMSC use. It also contributes to the broader IR discipline by proposing a change in perspective: away from an atomistic focus on norms to a more holistic study of legitimacy and legitimation. The resulting framework is particularly fruitful for the analysis of other controversial issues of international relations