The Involvement of Mercenaries and Private Military Security Companies in Armed Conflicts: What does IHL Say?

First of all, it is necessary to distinguish between private military security companies (PMSCs) and mercenaries. PMSCs are private business entities that provide military or security assistance to states, companies, or other organizations. On the other hand, mercenaries are defined in Article 47 of Additional Protocol I to the Geneva Conventions (AP I). It should be noted that seldom the staff of PMSCs can be considered a mercenary as defined in AP I.

IHL does not prohibit the use of PMSCs and mercenaries during armed conflicts. Nevertheless, two conventions ban the use of mercenaries in armed conflicts: the 1977 Organisation of African Unity Convention for the Elimination of Mercenarism in Africa and the 1989 International Convention against the Recruitment, Use, Financing and Training of Mercenaries. These conventions criminalize not only the resort to mercenaries but also the participation in armed conflicts as a mercenary.

Under IHL, staff of PMSCs and mercenaries as considered civilians. This means that they have no right to directly participate in hostilities and, if captured, they are not entitled to prisoner of war status. In any case, this does not mean that they are never protected under IHL, as they enjoy the protection granted by the Fourth Geneva Convention to civilians.

Just like civilians, PMSCs staff and mercenaries are not legitimate targets unless and for such time as they take direct participation in hostilities. However, this is particularly challenging with regard to PMSCs that have only defensive functions, as it is often the case: how to distinguish between acts of self-defence and direct participation in hostilities?

The question is crucial because PMSC staff is a lawful target only if they take direct participation in hostilities, not during self-defence activities. While the debate is still open, it should be noted that even defensive functions may amount to an armed attack as defined in IHL (Article 49 AP I), and hence qualify as direct participation in hostilities.

Just like all actors present in a country affected by an armed conflict, IHL is applicable to PMSCs staff and mercenaries, who are therefore bound by IHL and are criminally responsible should their conduct amount to war crimes.

Specifically, with regard to PMSCs, the Montreux Document is a non-binding inter-state instrument that aims at guiding states in their use of PMSCs. Furthermore, the International Code of Conduct for Private Security Service Providers (ICoCa) is the only instrument that lists the obligations of PMSCs. The main PMSCs have signed the document and have committed to implementing its obligations.

Generally speaking, PMSCs are not a party to the conflict. As mentioned before, their staff may qualify as civilians taking direct participation in hostilities, should their actions qualify as direct participation in hostilities (Article 51(3) of AP I, Article 13(3) of Additional Protocol II).

The only case when a PMSC could be a party to an armed conflict would be if the company itself started engaging in hostilities as an autonomous party, i.e. not as providing a service to a client. In this case, it would be necessary to assess whether the two criteria required by IHL are met, namely (1) the violence between the PMSC and the adverse party needs to meet the threshold of intensity and (2) the PMSC must be sufficiently organized.