The involvement of Private Security Companies (PSCs) adds an array of legal dimensions to the complexity surrounding multinational military operations. For the purposes of this chapter, a PSC is taken as a private, usually for-profit, company offering security-related services which include potentially lethal activities involving the possession and use of weapons and firearms.
At the core of the legal disruption introduced by the PSC is the dissociation between state action and the obligations under international humanitarian and human rights law obligations (IHL and IHRL respectively). Hitherto, the state’s organisational monopoly on the use of legitimate force and the international nature of these legal fields has rendered this conflation as relatively unproblematic. The introduction of the PSC, however, has left this heuristic increasingly untenable. First, the law has failed to unambiguously marginalise, let alone criminalise, the provision of martial services by private corporations. Secondly, while the argument that a strong international norm against mercenary activity manifested itself as weak law has been prevalent in international relations work, this perspective has recently sustained systemic challenge. Finally, with principled and consistent objections difficult to formulate against the private provision of organised force, reliance has been placed in residual categories that focus upon conduct in hostilities: excessive uses of force and human rights violations by private security contractors on the field. Taken together, the opprobrium directed against organised private violence as manifested in the PSC can be difficult to articulate coherently thereby leaving ample space for the PSC industry to argue their legitimacy. Indeed, Kofi Annan famously contemplated the imperative for engaging PSCs in peace operations in the absence of competing alternatives:

Some have even suggested that private security firms, like the one which recently helped restore the elected President to power in Sierra Leone, might play a role in providing the United Nations with the rapid reaction capacity it needs. When we had need of skilled soldiers to separate fighters from refugees in the Rwandan refugee camps in Goma, I even considered the possibility of engaging a private firm. But the world may not be ready to privatize peace.

There are significant pressures for employing PSCs in multinational military operations, including peace operations, in an environment of increasing military outsourcing. These are primarily the perceived capacity to fulfil of important humanitarian functions which have been neglected by traditional actors, and increased market pressures arising from the end of major conflicts in the Middle East. Given the myriad of ambiguities surrounding the employment of PSCs in multinational military operations, this chapter only explores some of the legal complexities arising from their involvement.