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Review 2018-2019 - Volume 57

Targeting Private Military and Security Companies
Head of Security and Law Programme, Geneva Centre for Security Policy

Table of Contents
  1. Introduction
  2. The Regulatory Framework
    1. Specific International Instruments
    2. Definition and Type of Services Offered
  3. Application of International Humanitarian Law to PMSCs
    1. The Right to Resort to PMSCs
    2. Status of PMSC and Implications for Targeting
  4. Direct Participation in Hostilities: Still a Debated Issue
  5. Direct Participation in Hostilities by PMSCs
    1. Limitations and Controversies
    2. Assessing Defensive Services in Light of DPH
    3. Practical Scenarios
  6. Targetability of PMSCs
  7. Conclusion

I. Introduction

Private Military and Security Companies (PMSCs) are private business entities whose activity consists of, or includes, the provision of services of a military and/or security character. Usually, they take the form of corporations. While private military companies broadly provide security services, private security companies limit their business to security services stricto sensu, excluding activities of a military nature. PMSC staff are commonly referred to as contractors to highlight the outsourced character of their services and to differentiate them from state armed forces.

The use of PMSCs has consistently expanded over the years. On the one hand, a growing number of states resort to PMSCs. On the other, states resorting to PMSCs use an increasing number of contractors. In recent armed conflicts, some states have used an equal share of contractors and uniformed personnel. 1 Furthermore, PMSCs are increasingly hired by non-state actors, especially humanitarian organisations and private companies, for the protection of persons or goods in volatile environments and conflict

* This article is an extended version of a presentation at the XII Seminar for Legal Advisors of the Armed Forces on “The Law of Armed Non-State Actors 70 Years after the Geneva Conventions” (June 2019), organized by the International Society for Military Law and the Law of War (ISMLLW) and the Geneva Centre for Security Policy (GCSP). The views expressed are the author’s alone and do not necessarily represent those of the above-mentioned institutions. The author thanks Tom Ruys, Stuart Casey-Maslen and Michael A. Rizotti for comments on earlier drafts as well as Alessandro Mario Amoroso for research assistance. Back
1 In Afghanistan and Iraq, for instance, contractors accounted for half of all personnel deployed by the US Department of Defence. See: M. Schwartz and J. Swain, Department of Defense Contractors in Afghanistan and Iraq: Background and Analysis (US, Congressional Research Service, 2011), p. 2. Back


areas. 2 This leads to the increasing “civilianization” of the armed forces and contemporary armed conflicts. 3

The phenomenon of PMSCs first raised international concern when two companies–Executive Outcomes and Sandline–provided combat forces and conducted full-scale military operations in the conflicts in Angola, Sierra Leone, and Papua New Guinea during the 1990s. 4 The direct outsourcing of the conduct of hostilities to PMSCs by states remains the exception, however, although the recent conflicts in Libya and Syria have witnessed the emergence of mercenaries and other armed non-state actors acting on behalf of states. 5 PMSCs gained public notoriety as a result of the Blackwater incident in Baghdad in 2007, in which seventeen civilians were killed during a shootout after one of Blackwater’s convoys was attacked while escorting an American diplomatic envoy. 6 This incident illustrated the common use of PMSCs for protection services, as well as the high potential for the use of lethal force by and against PMSCs. Yet, most of the state-mandated PMSC activity in conflict zones concerns logistics. Although such functions do not imply the use of force, these are crucial components of modern military operations.

The increasing use of PMSCs raises the question of their legal status. Given the close cooperation between states and PMSCs in conflict zones, as well as PMSCs’ support to reaching military objectives, it is of particular interest if PMSCs can be lawfully targeted by parties to an armed conflict. Notably relevant for planners and operators, this has not been addressed, as such, in the existing literature. This article examines these questions. After outlining the general normative framework and related debates, it analyses the conditions under which PMSCs directly participate in hostilities (DPH). It then discusses conceptual limitations, notably regarding the nexus between DPH and the defence of others, and proposes practical dividing lines between defensive services which amount to DPH and those that do not. It then applies the legal tenets to different scenarios. The article concludes by applying the targeting rules under international humanitarian law (IHL) to attacks against PMSC staff.

II. The Regulatory Framework

1. Specific International Instruments

PMSCs’ activities are regulated on three levels. The contractual relation between a state and a PMSC is first regulated by a specific contract. Second, the employment of PMSCs is normally regulated by domestic legislation and regulations of the contracting state. PMSCs are generally also regulated by the domestic legislation of the state in whose jurisdiction the activities are executed. At the international level, there are currently no legally binding instruments specifically governing PMSCs. A series of initiatives in this regard, however, have been undertaken.

The United Nations (UN) Working Group on Mercenaries prepared a draft Convention on the Regulation, Oversight and Monitoring of Private Military and Security Companies. 7 The draft convention, which requires states to adopt national legislation to regulate PMSCs, was presented to the Human Rights Council. The Council did not adopt the draft convention, however, because it lacked

2 A prominent example of PMSCs protecting private entities is the protection of ships. See, e.g.: The Financial Times, ‘Securing ships: from Somali pirates to Gulf to Oman tanker attacks’, 19 June 2019, Back
3 G. Bartolini, ‘The “Civilianization” of Contemporary Armed Conflicts’ in H. Ruiz Fabri et al. (eds), Select Proceedings of the European Society of International Law’ (London, Hart, 2008), Vol. II, pp. 569–595; International Committee of the Red Cross, International Humanitarian Law and the Challenges of Contemporary Armed Conflicts (Geneva, 2007), p. 15. Back
4 L. Cameron and V. Chetail, Privatizing War: Private Military and Security Companies under Public International Law (New York, Cambridge University Press, 2013), p. 2. Back
5 The Arab Weekly, ‘Tripoli militias said to be receiving help from foreign mercenaries’, 26 April 2019, ; Th. Gibbons-Neff, ‘How a 4-hour Battle Between Russian Mercenaries and US Commandos Unfolded in Syria’, 24 May 2018, New York Times, ; and BBC News, ‘Syria War: Who are Russia’s Shadowy Wagner Mercenaries?’, 23 February 2018, Back
6 BBC news, ‘Blackwater incident: What happened’, 8 December 2008. Back
7 UN Doc A/HRC/15/25. Back


support by states relying on PMSCs, primarily Western states. To continue the efforts in this regard, the Human Rights Council established an open-ended intergovernmental working group. Thus far, it has failed to produce concrete results. 8

Absent any legally binding convention, the normative framework at the international level particularly consists of soft law. The 2008 Montreux Document on Pertinent International Legal Obligations and Good Practices for States Related to Operations of Private Military and Security Companies During Armed Conflict (Montreux Document) 9 is a politically binding document addressed to states. It recalls the existing legal obligations of states–contracting states, home states, host states, and all other states–and companies providing security services. Obligations are drawn from both IHL and international human rights law (IHRL). This includes the obligation of contracting states to ensure that PMSCs are aware of and trained in IHL. 10 The Montreux Document also outlines good practices for states to promote compliance with international law during armed conflicts through due diligence obligations. 11

Industry adopted in 2010 the International Code of Conduct for Private Security Service Providers (ICoC). 12 It is a set of principles open to signature by private security companies. The ICoC is binding for signatory companies but does not operate at the inter-state level. It articulates companies’ human rights responsibilities for the provision of private security services, particularly when operating in complex environments. The ICoC Association (ICoCA) works as a multi-stakeholder supervisory and governance mechanism. Initially encompassing 700 companies, the number has dropped to approximately 100 because smaller companies could not bear the financial burden of membership in the ICoCA. 13

2. Definition and Type of Services Offered

Although PMSC became a term of art in international law, notably in IHL, there is no definition of PMSC in any legally binding international instrument. Some countries regulate the actors or related activities in their national law. As a result, PMSCs have differing definitions in domestic systems. 14 A debated feature is whether military and security services must constitute the core business of the private entity, or can simply be an activity within a wider range of services provided by the company.

The Montreux Document (point 9a) provides the following definition of PMSCs: “PMSCs are private business entities that provide military and/or security services, irrespective of how they describe themselves. Military and security services include, in particular, armed guarding and protection of persons and objects, such as convoys, buildings and other places; maintenance and operation of weapons systems; prisoner detention; and advice to or training of local forces and security personnel.” 15 The ICoC only uses the first sentence of point 9a of the Montreux Document as its definition of PMSC. 16

In line with the Montreux Document’s definition, PMSCs provide a vast array of services, including base support (such as maintaining the grounds, running dining facilities, and performing laundry services); transport support and other logistics (such as construction and convoy driving); translation; training armed and police forces; the provision of advice; intelligence gathering; espionage and counterespionage; programming and maintaining weapons systems; mine clearance; checking, detention, or searching of persons; searching of premises and seizure of objects; protection of persons;

8 HRC/NONE/2018/40, p. 25. Back
9 Montreux Document on Pertinent International Legal Obligations and Good Practices for States Related to Operations of Private Military and Security Companies During Armed Conflict, 2008. Back
10 Id., Part I. Back
11 Id., Part II. Back
12 International Code of Conduct for Private Security Service Providers, 2010. Back
13 For more information, see the ICoCA website: Back
14 For an example, see the Swiss Federal Act on Private Security Services provided Abroad (PSSA) of 27 September 2013, Article 2. For more examples of national laws and other regulations, see the HRC’s sample at: Back
15 Montreux Document, supra note 9, § 9(a). Back
16 See: Back


protection, guarding or surveillance of objects and transports; guarding, caring for, and transporting prisoners; operating prison facilities; as well as assisting in operating prisoner camps.

While many of these activities have a military character or have a link to military operations, most PMSCs active in conflict zones are not engaged for military tasks. In Iraq, for instance, the great majority (60%) of contracted personnel hired by the US Department of Defence carried out base support services. Another 10% were employed in other logistics activities. Less than 20% of all contractors were tasked with protection and security services. 17

Important from a legal point of view is that none of the listed activities implies the deliberate outsourcing of the use of force for the conduct of hostilities against an enemy. PMSC activity in conflicts and unstable environments may lead to situations in which contractors employ force, notably when they defend themselves or persons and objects that they are mandated to protect. Yet, contracts instructing and requiring PMSCs to use force in the conduct of hostilities are rare. Mercenaries hired by the Gadhafi regime to combat rebel groups 18 as well as PMSCs allegedly mandated by Russia in the Syrian conflict 19 remain a recent yet until now isolated phenomenon.

III. Application of International Humanitarian Law to PMSCs

1. The Right to Resort to PMSCs

IHL governs the status of persons and objects as well as the conduct of hostilities in armed conflicts. A preliminary question is whether IHL allows the use of PMSCs, i.e. if states have a right–the legal faculty–to resort to PMSCs. Modern IHL was shaped in an era marked by state monopoly over the use of force in warfare. Thus, unsurprisingly, it does not directly address PMSCs. The result is that IHL does not provide an explicit authorization to employ PMSCs in warfare or to outsource war-related activities, nor is there any explicit general prohibition.

There are exceptions, however, where IHL explicitly requires state officials to execute certain tasks which cannot be delegated to non-state actors unless they are integrated into the state armed forces. The most important task that cannot be outsourced is the role of responsible officer of a prisoners of war (POW) camp, who must be a commissioned officer belonging to the regular armed forces of the detaining power. 20 Disciplinary punishment in POW camps may also be ordered only by an officer having disciplinary powers in his capacity as camp commander, or by a responsible officer who replaces him or to whom he has delegated his disciplinary powers. 21 Furthermore, places of internment for civilians shall be put under the authority of a responsible officer, chosen from the regular military forces or the regular civil administration of the detaining power. 22

Other roles in POW and internment camps, such as construction and maintenance, as well as guarding prisoners, can be delegated by states to PMSCs. Yet Pictet’s commentary on the Third 1949 Geneva Convention clearly indicates that private employees may never use weapons against prisoners, except in personal self-defence, since this would amount to an act of war which could only be performed by state officers. 23 Hence, PMSC personnel guarding POWs or assisting guards of prisoners of war would not be able to use force against a prisoner who is trying to escape. 24 Furthermore, IHL also explicitly

17 Schwartz and Swain, supra note 1, p. 16. Back
18 A. Mahjar-Barducci, ‘Gaddafi’s Mercenaries in Libya’, 30 March 2011, See also: supra note 5. Back
19 Supra note 5. For a legal and empirical analysis of the PMSC called Wagner Group, see: M. A. Rizotti, ‘Mercenaries in Syria? Wagner Group Activities Examined Through the Lens of International Law’, unpublished working paper. Back
20 GC III, Article 39. Back
21 GC III, Article 96. Back
22 GC IV, Article 99. Back
23 GC III, Article 42; International Committee of the Red Cross, Pictet Commentary to the Geneva Convention III (Geneva, 1960), p. 248. Back
24 It is noteworthy that all these limitations regarding POW and internment camps are only applicable to international armed conflicts. Back


prohibits states from outsourcing demanding requisitions in kind and services in an occupied territory. 25 Finally, private ships cannot intercept and capture enemy ships and their cargo. 26

Some legal experts contend that the rationale and functioning of the IHL regime would not allow outsourcing the conduct of hostilities to private actors altogether. Cameron and Chetail argue that this would inevitably put the state in violation of the main IHL principles governing the conduct of hostilities, namely the principles of necessity, proportionality, and distinction. 27 PMSCs would not be able to properly assess criteria such as the military advantage anticipated from an attack (a constitutive element of the principle of proportionality), military necessity, or security reasons. To evaluate these substantive criteria, a certain level of integration in a state organisation and a chain of command would be required. 28 A state mandating a group of civilians to conduct military operations on a permanent basis would also breach the duty of combatants to distinguish themselves from civilians. 29 This reasoning seems to overstate IHL’s requirements, however, as this would also exclude other armed non-state actors, such as rebel groups, from properly applying IHL. Furthermore, PMSCs may well distinguish themselves from the civilian population.

Looking into other branches of international law, IHRL does not prohibit the outsourcing of law enforcement tasks such as policing and detention as long as the same human rights standards applicable to state officials are ensured. It does, however, contain an implicit prohibition to delegate the exercise of criminal justice. This must always be undertaken by a state official. 30

In sum, states can outsource war-related activities to PMSCs with some exceptions. 31 When they do so, this leads adversaries to the crucial question: Can PMSC staff be targeted? The basic rule applicable to targeting, Article 48 of the Additional Protocol I to the Geneva Conventions (AP I), says that only military objectives can lawfully be attacked. Regarding PMSCs, absent explicit regulation under IHL, the answer is less straight-forward. It is informed by how IHL applies to PMSCs and their staff.

2. Status of PMSC and Implications for Targeting

PMSCs can fall under IHL by various means. PMSCs can be bound through self-regulation, namely through codes of conduct, or the contract with the mandating state. Some authors argue that the doctrine of corporate responsibility would also allow applying IHL to PMSCs to the extent that they are recognised as subjects of international law. 32 IHL and international criminal law include rules which are directly applicable to individuals to the extent that they concern conduct that must be sanctioned by states as crimes. This also means that IHL at the very least binds PMSC staff when they commit international crimes. As PMSCs are the sum of their individual employees, they are also subject to those rules. 33 This does not clarify, however, the legality of targeting them.

PMSC staff are subject to IHL to the extent they fall in the categories of mercenaries, combatants, persons accompanying armed forces, members of organized armed groups, and regular civilians. For international armed conflicts, Article 47 of the Additional Protocol I provides the definition of mercenaries. This requires, among other conditions, that mercenaries are recruited to fight and that they are not nationals of one of the parties to the conflict. Mercenaries have recently been used in the Libyan conflict and to some extent in Syria. 34 PMSC staff engaged in modern conflicts generally do not fulfil

25 1907 Hague Regulations, Article 52. Back
26 Paris Declaration Respecting Maritime Law, France, 16 April 1856. Back
27 Cameron and Chetail, supra note 4, pp. 91–107. See also: M. Sassòli, International Humanitarian Law: Rules, Controversies, and Solutions to Problems Arising in Warfare (Cheltenham, Edward Elgar, 2019), p. 548. Back
28 Sassòli, supra note 27, p. 548; Cameron and Chetail, supra note 4, pp. 95–96. Back
29 Cameron and Chetail, supra note 4, p. 104. Back
30 Cameron and Chetail, supra note 4, p. 125. Back
31 When they do so, states retain their IHL obligations and can be responsible for violations committed by PMSCs. This is reflected in the Montreux Document, supra note 9, Section A(1). Back
32 Cameron and Chetail, supra note 4, pp. 289. Back
33 Cameron and Chetail, supra note 4, pp. 355–362. Back
34 J. Hammond, ‘Foreign Fighters and Mercenaries Fueling Libyan Conflict’, 2 January 2018,; and A. Luhn and D. Nicholls, ‘Russian Mercenaries Back Libyan Rebel Leader as Moscow Seeks Influence in Africa’, 3 March 2019, See also: supra note 5. Back


the very narrow conditions of Article 47 of the Additional Protocol I, however, as they are mostly not mandated to conduct hostilities and are oftentimes not foreign nationals. US forces, for instance, substantially cooperated with American contractors in the recent conflicts in Afghanistan and Iraq. 35 In any case, for targeting purposes, as mercenaries do not have combatant status, they can only be targeted when they directly participate in hostilities. 36

PMSC staff can qualify as combatants that can be lawfully targeted both in international and non-international armed conflicts. Article 4A(1) of the Third Geneva Convention applies to PMSC staff that are formally incorporated members of the armed forces as well as members of militias or volunteer corps forming part thereof. While IHL does not provide clear and specific guidance for determining this status, 37 PMSCs are generally not incorporated into armed forces to the extent necessary under Article 4(A)1, notably because states’ rationale for using them is to reduce numbers of armed forces and related costs. 38 PMSC staff can also fall under the category of Article 4A(2), namely members of groups that are not formally associated to armed forces but fight alongside them. The International Tribunal for the former Yugoslavia (ICTY) held that the state party to the conflict would need to have control over these groups and there would need to be a relationship of dependence and allegiance. 39 Such groups also need to be commanded by a person responsible for its subordinates, have a fixed distinctive sign, carry their arms openly, and conduct their operations in respect of IHL. In practice, PMSCs rarely fulfil all these conditions, however. Article 43 of the Additional Protocol I complements Article 4A(2). While it is more easily applicable to PMSCs as it does not require the latter’s four conditions, it demands a stronger link between the PMSC and the state party to the conflict: The PMSC would need to be “under the command responsible to that Party” rather than just “belong to” a party to an armed conflict.

PMSC staff may also fall under the category of persons accompanying armed forces according to Article 4(A)(4) of the Third Geneva Convention, provided the procedural requirements of this provision are fulfilled: “Persons who accompany the armed forces without actually being members thereof, such as civilian members of military aircraft crews, war correspondents, supply contractors, members of labour units or of services responsible for the welfare of the armed forces, provided that they have received authorization from the armed forces which they accompany, who shall provide them for that purpose with an identity card similar to the annexed model.” The list of roles and professions is clearly non-exhaustive. Such persons receive POW status when they fall into the power of the enemy. Note that this category of persons is explicitly excluded from the notion of combatants, as can be derived from Article 50 of the Additional Protocol I: “A civilian is any person who does not belong to one of the categories of persons referred to in Article 4 A (1), (2), (3) and (6) of the Third Convention and in Article 43 of this Protocol.” Thus, when PMSC staff qualify as persons accompanying the armed forces as per Article 4(A)(4) of the Third Geneva Convention, they are considered as civilians without the right to participate directly in hostilities and are in principle protected from direct attack.

In non-international armed conflicts, PMSC that engage in fighting on a regular basis can constitute an independent organized armed group. According to the ICTY Trial Chamber in the Boškoski case, to be a party to an armed conflict, such groups need to be sufficiently organized. Necessary features are a command structure, the ability to carry out operations in an organized manner, the level of logistics, the level of intra-group discipline, and the ability to “speak with one voice”. 40 PMSCs can readily satisfy these criteria. An example of a PMSC plausibly falling under the category of organized armed group is

35 Schwartz and Swain, supra note 1, pp. 10–13. Back
36 See in this regard: Section IV and V. Back
37 For a suggestion of indicators related to PMSCs, see: E.-C. Gillard, ‘Business Goes to War: Private Military/Security Companies’, Vol. 88, No. 863, International Review of the Red Cross, 2006, p. 533. Back
38 M. Schmitt, ‘Humanitarian Law and Direct Participation in Hostilities by Private Contractors or Civilian Employees’, Vol. 5, No. 2, Chicago Journal of International Law, 2005, p. 526. Back
39 ICTY, Appeals Chamber, The Prosecutor v. Dusko Tadic, IT-94-1, Judgment, 15 July 1999, §§ 93–94. Back
40 ICTY, Trials Chamber, The Prosecutor v Ljube Boškoski & Johan Tarčulovski (IT-04-82), 10 July 2008, §§ 199–2013. Back


the Wagner Group, which operated in the Syrian conflict. 41 A PMSC can also act on the instructions and under the direction or control of an organized armed group itself party to a non-international armed conflict. In this case, the PMSC’s actions are attributed to the organized armed group. 42 The legal scope for targeting members of organized armed groups is controversial. A membership approach, notably applied by the United States of America, allows states to target any member of organized armed groups at any time. This would be justified by the fact that members of regular armed forces are also targetable at any place and time under IHL, even when tasked with cooking or when sleeping, for instance. 43 The ICRC, however, suggests a functional approach. It argues that only those members of organized armed groups with a “continuous combat function” can be directly attacked at any time. 40 This notion is contested, however.

All other PMSC staff–persons that under IHL are not mercenaries, nor combatants, nor persons accompanying armed forces, nor members of organized armed groups–qualify as civilians. The most important consequence of this status is that they are generally entitled to protection against attacks. PMSCs falling under this category – the majority of those currently employed in conflict zones – may thus not be attacked. 45 As for any civilian, however, this protection ceases if PMSC personnel directly participates in hostilities, for the time they do so. Since PMSC staff in conflict zones are mostly civilians engaged in war-related activities, the concept of direct participation in hostilities has a particular relevance for their legal situation and targetability.

IV. Direct Participation in Hostilities: Still a Debated Issue

Under IHL, when civilians directly take part in hostilities, they relinquish their protection and, consequently, can be attacked. Article 51 of the Additional Protocol I states that: “Civilians shall enjoy the protection […], unless and for such time as they take a direct part in hostilities.” 46 In addition to international armed conflicts, DPH can also occur in non-international armed conflicts. 47 The loss of protection is temporary: civilians regain protection as soon as their engagement in a hostile act ends and they resume their normal activities (so-called “revolving door” mechanism). Since they do not enjoy combatant privilege, civilians directly participating in hostilities may be prosecuted according to the domestic legislation of the state where the action happens. They do not qualify for prisoner of war status when captured in international armed conflicts, unless they are accompanying armed forces according to Article 4(A)(4) of the Third Geneva Convention. 48

IHL does not provide a definition of DPH. The International Committee of the Red Cross (ICRC) proposed in 2009 an Interpretive Guidance on the notion of DPH. 49 The ICRC Guidance defines DPH by three constitutive elements which must be cumulatively met for a specific act to qualify as DPH:

41 Rizotti, supra note 19. Back
42 N. Melzer, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law (Geneva, ICRC, 2009), pp. 39–40; International Committee of the Red Cross, ‘Third Expert Meeting on the Notion of Direct Participation in Hostilities’ (Geneva, 2005), p. 82. Back
43 See, e.g.: G. Gaggioli, The Use of Force in Armed Conflicts: Interplay between the Conduct of Hostilities and Law Enforcement Paradigm (Geneva, ICRC, 2013). Back
44 Melzer, supra note 42; N. Melzer, ‘Keeping the balance between military necessity and humanity: a response to four critics of the ICRC’s interpretive guidance on the notion of direct participation in hostilities’, Vol. 42, No. 697, Journal of International Law and Politics, p. 845. Back
45 API, Article 51(2), 57; APII Article 13(2); Customary rule 1 (both in IAC and NIAC); CCW API Article 3(2); Amended CCW Protocol II Article 3(7) and Amended CCW Protocol III Article 2(1); Preamble of the Ottawa Convention. In the Kassem case in 1969, Israel’s Military Court at Ramallah recognized the immunity of civilians from direct attack as one of the basic rules of international humanitarian law (Israel, Military Court at Ramallah), §271. Back
46 API, Article 51(3). Back
47 For non-international armed conflicts, see Common Article 3 GCsI-IV and APII, Article 13(3). Back
48 This is not the case when PMSCs fulfil the criteria for combatant status provided under in API, Article 44(3). Note also that API does not enjoy universal ratification and that Article 44 specifically is the object of dispute. Its customary character is normally denied. In practice, it is very improbable that PMSC staff fulfil the conditions of API, Article 44(3). Back
49 Melzer, supra note 42. Back


  1. Threshold of harm: the act must be likely to adversely affect the military operations or military capacity of a party to an armed conflict or, alternatively, to inflict death, injury, or destruction on persons or objects protected against direct attack;
  2. Direct causation: there must be a direct causal link between the act and the harm likely to result either from that act, or from a coordinated military operation of which that act constitutes an integral part; in other words, the contribution to the hostilities must meet the threshold of harm in one causal step;
  3. Belligerent nexus: the act must be of a nature to cause the required threshold of harm in support of a party to the conflict and to the detriment of another. 50
This conceptualization attaches DPH to specific acts committed by a civilian. DPH therefore does not depend on the status, function or affiliation of that person. In other words, while the notion of combatant is status-based, that of a civilian directly participating in hostilities is grounded in an activity-based assessment.

The ICRC Guidance offers the institution’s understanding of DPH but its positions do not enjoy unanimous acceptance. The ICRC Customary International Humanitarian Law study acknowledges that outside a few uncontested examples, “in particular the use of weapons or other means to commit acts of violence against human or material enemy forces, a clear and uniform definition of direct participation in hostilities has not been developed in State practice.” 51

Part of the discussions revolves around what is meant by hostile act. The ICRC Commentary on the Additional Protocol I defines hostile acts as “acts which by their nature and purpose are intended to cause actual harm to the personnel and equipment of the armed forces.” 52 Yet, it remains ambiguous what makes participation in hostilities “direct”. The Inter-American Commission on Human Rights and the Supreme Court of Israel agreed that: “It is generally understood in humanitarian law that the phrase ‘direct participation in hostilities’ means acts which, by their nature or purpose, are intended to cause actual harm to enemy personnel and material.” 53 This would not imply that the concept of direct participation is limited to those who bear arms, however. 54

The temporal scope of the loss of protection is another controversial issue in the definition of DPH. 55 Although PMSC staff, different from normal civilians, are likely to commit more than isolated acts of DPH, their actions amounting to DPH must always be considered on an individual basis to decide whether the person is temporarily engaging in DPH for the relevant time. Recurrent direct participation in hostilities cannot be summed up for a continuous loss of protection. This creates the so-called “revolving door” mechanism which is highly contested. It is disputed that such a rule–which would create unequal standards between combatants (who can be targeted at any time and place) and its non-state adversaries–would exist in law. 56 That said, in a non-international armed conflict, all those who engage in hostilities against government armed forces are subject to domestic prosecution, which means the playing field is hardly level.

50 Id., Part V, Constitutive Elements of Direct Participation of Hostilities, p. 46. Back
51 J. Henckaerts and L. Doswald-Beck, Customary International Humanitarian Law: Volume 1: Rules (Geneva, ICRC, 2005), p. 23. Back
52 Y. Sandoz, Ch. Swinarski and B. Zimmermann, Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 (Geneva, ICRC, 1987), § 1942. Back
53 Inter-Am. C.H.R., Third Report on the Human Rights Situation in Columbia (OEA/Ser.L/V/II.102, Doc. 9 Rev. 1 Ch. 4), 26 February 1999, § 53, and HCJ 769/02, Pub. Comm. Against Torture in Israel v. Gov’t of Israel (Targeted Killings), Judgment, 11 December 2005, § 33. Back
54 D. Akande, ‘Clearing the Fog of War? The ICRC’s Interpretive Guidance’, 4 June 2009, Back
55 According to the ICRC Guidance, civilians may be subject to a continuous loss of protection only if they have been assigned the continuous function to take direct part in the hostilities on behalf of a party to the conflict. It can be said that in this case they exercise a continuous combat function (CCF). CCF is a function-based notion. See: N. Melzer, supra note 42, pp. 31–35. As outlined above, PMSCs are mostly not mandated to fight, however. Back
56 M. Schmitt, ‘Deconstructing Direct Participation in Hostilities: The Constitutive Elements’, Vol. 42, No. 3, New York University Journal of International Law and Politics, 2010, p. 697. Back


There are further controversies, such as the definition of civilians in non-international armed conflicts. The ICRC Guidance holds that members of organized armed groups do not qualify as civilians. To some, this was going too far in that it created a new group of individuals who were neither classified as civilians nor combatants, as there is no combatant status as such in non-international armed conflicts. Others considered it did not go far enough and argued that any member of the armed group to which the person directly participating in hostilities belongs should be targetable. 57 This debate affects notably policies on targeted killing of members of terrorist organizations. The U.S. government grounds its legal basis on the second perspective, i.e. it also targets members of organized armed groups that do not or did not directly participate in hostilities. 58 Another open question regarding DPH is to what extent a child’s activity amounts to DPH. 59

V. Direct Participation in Hostilities by PMSCs

1. Limitations and Controversies

PMSC activity gives rise to operational scenarios in which the limits of the ICRC Guidance become apparent. This is notably the case when they provide services for which they put themselves at high risk in conflict zones and when they are equipped with firearms.

First, the ICRC Guidance envisages the possibility of applying the notion of continuous combat function to private contractors. It considers that in this case, PMSCs would de facto be incorporated into the armed forces of a state as an organised armed group under a command responsible to a party to the conflict. 60 They would therefore no longer qualify as civilians. Some authors argue that this scenario may go against the underlying rationale of IHL prohibiting states to outsource the conduct of hostilities to private actors. 61 More importantly, from a factual perspective, PMSCs are mostly not mandated to fight. This would imply that only very few members of PMSC could be targeted according to the approach on continuous combat function. All others could be targeted only when directly participating in hostilities. Given the difficulty to assess when PMSC personnel directly participate in hostilities, and when they do not, states may be tempted to adopt the membership approach for targeting PMSCs, i.e. are willing to target any member of a PMSC, as is done against terrorist groups.

Second, in collective operations, only a few persons carry out acts that, individually considered, would amount to DPH, such as the delivery of force during a military operation. Yet many others engage in conduct that constitutes an integral part of a concrete and coordinated tactical operation which directly causes the required harm in one causal step. The ICRC guidance suggests that these actions qualify as DPH only if the act is part of a specific operation. 62 PMSCs are rarely contracted to fight but oftentimes effectively contribute to collective operations. As general contributions to collective operations of strategic importance can be essential factors for operational success, this can be perceived from a military perspective as an unsatisfactorily high threshold.

Third, one of the most disputed issues concerns the distinction between activities amounting to DPH, on the one hand, and the use of force in self-defence and defence of others, on the other. Indeed, since cases of PMSCs mandated to conduct hostilities are uncommon, the most likely scenario implying a high risk to commit DPH is the protection of persons and objects. When PMSCs are confined to this activity, only defensive functions are assigned. According to the ICRC Guidance, actions undertaken in self-defence or defence of others do not amount to DPH because the defence of the self or of others

57 C. Garraway, ‘The Changing Character of the Participants in War: Civilianization of Warfighting and the Concept of “Direct Participation in Hostilities”’, Vol. 87, No. 1, International Law Studies, 2016, p. 180. Back
58 K. Anderson, ‘Targeted Killing in US Counterterrorism Strategy and Law’, 6 June 2009, Back
59 J. Yuvaraj, ‘When Does a Child ‘Participate Actively in Hostilities’ under the Rome Statute? Protecting Children from Use in Hostilities after Lubanga’, Vol. 32, No. 83, Utrecht Journal of International and European Law, 2016, pp. 69–93. Back
60 Melzer, supra note 42, pp. 37–40. See in this regard: Section 2. Back
61 Sassòli, supra note 27, p. 548; Cameron and Chetail, supra note 4, pp. 91–107. Back
62 Melzer, supra note 42, pp. 54-55 and 65. Back


precludes the existence of a belligerent nexus. The ICRC Guidance in other words equates self-defence and defence of others, giving the impression that they are subject to the same legal regime.

Legitimate self-defence can never constitute DPH. Defending others can do so, however, depending on the status of the person or object protected by the PMSC. 63 As a result, while all PMSC staff enjoy an inherent right of self-defence, it cannot be said that they also have a right to defend others, at least not if by right it is meant that they would escape the qualification as DPH. This derives from the source of these rights. The right to defend yourself stems from a person’s right to life under international human rights law. Conversely, the right to defend others is normally grounded in domestic criminal law of the contracting state or the territorial state. It is controversial, however, that domestic law can give the right to use force not amounting to DPH under IHL. 64 It is also debated whether combatants, as well as civilians directly participating in hostilities, have a right to self-defence. 65 This discussion is not relevant regarding the targeting of PMSCs, however, because PMSCs defending themselves does not amount to DPH, and those directly participating in hostilities can be targeted no matter their right to self-defence.

Finally, under IHL, a defensive action might well legally qualify as an attack and amount to direct participation in hostilities. Indeed, in IHL there is no difference between offensive and defensive attacks. 66 Thus, what matters for defining the legality of an attack is the status of the person or object that is protected, not the status of the attacker. 67 Accordingly, defending civilians and civilian objects from attacks, as well as defending combatants and military goods from common criminality, i.e. an action with no nexus to the armed conflict, does not amount to DPH. Conversely, defending combatants or military objectives from their adversary does result in DPH because they are legitimate targets and there is a clear belligerent nexus. This is also the case if the attacker does not benefit from the combatant privilege, i.e. is not entitled to engage in the conduct of hostilities: the unlawful status of the attacker has no bearing for this assessment. Yet for both PMSC staff and parties to the conflict, these distinctions are extremely difficult to make in tense and dangerous situations or even battle. It can be impossible for them to know whether the object they are protecting is or has turned into a legitimate military objective, whether the attacker engages in a criminal activity or action favouring a party to the conflict, and whether the defensive use of force is perceived as an attack by the opponent.

2. Assessing Defensive Services in Light of DPH

The use of defensive force does not amount to DPH when it is carried out to repulse unlawful attacks because this lacks a belligerent nexus. The criteria of causality and harm are satisfied by definition since the defender uses force to repel the attack. The question hence reverts to the determination of when an attack is unlawful. 68 Such unlawfulness must be assessed under IHL, not domestic criminal law. Although an attack can be unlawful under IHL on several bases, only the legal status of the attacked person or object–in accordance with the principle of distinction–defines the legality of the attack for the purpose of distinction between DPH and the legitimate defence of others. The legal status of the attacker, i.e. somebody enjoying or not enjoying combatant privilege, the respect of the proportionality rule and the duty to take precautionary measures, as well as the legality of the used means and methods of warfare, are not enough to make the whole attack unlawful for the purpose of differentiating between DPH and the legitimate defence of others. The reason for this is that these legal elements of an attack are not related to the belligerent nexus.

63 This is the solution proposed by Schmitt, supra note 38, pp. 538–539. Cameron and Chetail, supra note 4, pp. 464–476, agree on the criterion. They substantially build on this interpretive proposal, showing also why other criteria cannot help assessing DPH. Back
64 Sassòli, supra note 27, p. 542 ; Cameron and Chetail, supra note 4, pp. 455–484. Back
65 Sassòli, supra note 27, p. 551. See also the Symposium on Soldier Self-Defense and International Law at OpinioJuris: Back
66 API, Article 49(1). Back
67 Cameron and Chetail, supra note 4, pp. 464–476. Back
68 Id. Back


From a practical view, the legal status of the person or object attacked is the determinate criterion to distinguish between DPH and the defence of others not amounting to DPH because a private contractor defending military personnel or military objectives from enemy attack frees up soldiers for other combat missions, thereby further contributing to hostile action. 69 This does not apply to the defence of others against criminality, as this is less demanding in combat resources. The consequence for targeting is the following: PMSCs defending others which leads to DPH are targetable, whereas PMSCs protecting others that does not lead to DPH are not targetable.

Practical dividing lines between defensive services which amount to DPH and those that do not are the following:
  • The defence or protection of military personnel and objectives or other legitimate targets, such as civilians directly participating in hostilities, against enemy attacks constitutes DPH;
  • The protection of military personnel and objectives and of other legitimate targets against common crime unrelated to the hostilities will not qualify as DPH, because the attack lacks a nexus with the armed conflict;
  • The protection of civilians–unless they directly participate in hostilities–and civilian objects against acts of violence, even carried out by enemy combatants, will not qualify as DPH. This normally constitutes the exercise of law enforcement functions, self-defence or defence of others. This is because attacks on civilians and civilian objects are always unlawful attacks lacking a belligerent nexus.
The use of force in self-defence or defence of others must, of course, also be necessary and proportionate. 70 It is open to debate whether the requirement of necessity also introduces a duty to retreat, if possible, when faced with a threat of attack. In any case, it is noteworthy that self-defence can only be exercised against attacks, not to resist arrest or prevent the adversary from gaining control over objects. These actions are lawful under IHL and hence cannot give rise to self-defence.

3. Practical Scenarios

Applying the above to practical scenarios allows for the illustration of conceptual boundaries. The most straightforward scenario is that of PMSC staff attacking combatants and military objectives. This clearly amounts to DPH because all three conditions for DPH are fulfilled. This is also the case when PMSCs use force to defend combatants and military objectives against an attack by a party to the conflict. However, if the attack takes place for motives unrelated to the conflict, the requisite nexus is absent and the conduct does not constitute DPH. 71 The same is true for PMSCs that conduct demining operations, such as in Iraq against mines laid by the Islamic State of Iraq and the Levant. If the demining generates an operational advantage to a party to the conflict, this constitutes DPH. Although demining does not produce any harm, it directly prevents damage to armed forces and supports military operations.

The protection of civilians generally does not amount to DPH. Yet, it can suddenly turn into an act of DPH if the civilian under protection directly participates in hostilities. In this case, the civilian under protection becomes a legitimate target; defending him would therefore be directly participating in hostilities, too. Similarly, in IHL every object can become a military objective according to the criteria of Article 52(2) of the Additional Protocol I, namely through its location, purpose, or use. It may happen that the military relevance of a location changes, for instance. PMSCs may be mandated to defend a civilian building that contains the archives of a village. If the building inevitably blocks the advancement of military forces in a way that its destruction offers a definite military advantage, the building becomes a military objective. Objects can also change their purpose, even without surrounding people realising it. A school defended by a PMSC becomes a military objective if the adversary is planning to headquarter its troops there, for instance. Therefore, objects previously classified as civilian objects

69 Schmitt, supra note 38, pp. 538–539. Back
70 See, e.g.: J. A. Hessbruegge, Human Rights and Personal Self-Defense in International Law (Oxford, Oxford University Press, 2017), pp. 255–268. Back
71 Schmitt, supra note 38, pp. 536–537. Back


might become military objectives. In this case, defending them against an attack by an adversary would constitute DPH.

While operating a weapons system does not present any substantial difference from any other method of conducting an attack, the maintenance of weapons systems is trickier to assess in light of DPH. Here, the ICRC guidance and Schmitt’s views seem to substantially differ. Under the ICRC guidance, maintenance qualifies as DPH when it is part of a “specific operation”. Conversely, for Schmitt, the same happens only if preparing equipment for battle has a “direct impact on the course of battle”. 72 His threshold for the maintenance of weapons system to qualify as DPH is therefore higher.

Most tasks performed by PMSCs are far removed from the actual hostilities, not only geographically but also temporally. For the qualification as DPH, the geographical or temporal proximity of an act is not relevant, however. This is particularly important for the provision of logistics, training, and weapons. In general, these actions do not amount to DPH. Yet they may constitute an act of DPH when they are part of a collective operation. If bombs are loaded onto an aircraft for an unspecified future use in airstrikes, this does not amount to DPH. If, conversely, the same action is realised to enable the aircraft to conduct a specific strike, even if the strike takes place after some time, loading the bombs does amount to DPH. This is the approach of the ICRC guidance, i.e. the act must form part of a specific collective operation to qualify as DPH. Schmitt, however, defends a narrower rule. Only “immediate” battlefield logistics functions, such as directly supplying troops engaged in combat with ammunition, would be DPH because such an action might determine the victor. 73

The same applies to training and military advice. If the training enables the execution of a predetermined hostile act, this constitutes an integral part of that act and, therefore, DPH. 74 Schmitt applies the same approach and explains: “if civilians are providing advice on the conduct of actual military operations at the tactical level, then they are directly participating because the flow of hostilities is greatly determined by their input. At the operational level, the evaluation of such advice would have to be conducted on a case-by-case basis. To the extent it involves the deployment of forces into combat for specific operations, it is likely to amount to direct participation. By contrast, merely offering general advice on military matters in the area of operations would not.” 75 The same is true for weapons supply. Delivering weapons systems, weapons and ammunition to a weapons storage does not amount to DPH, whereas delivering to active firing positions would because an integral part of a specific combat operation.

Planning is one of the activities which are not specifically considered by the ICRC guidance but that at the same time can involve PMSCs, especially when their advice is sought. Schmitt proposes a strategic/operational/tactical paradigm of decision-making: while the involvement of civilian decision-makers at the strategic level is common and even an essential feature in democracies, “all tactical level planning, such as mission planning for aerial operations, amounts to direct participation because specific military operations could not occur but for that planning.” 76 Once again, the standard applied is that of a contribution to a specific military operation. “The same is generally true of operational level planning regarding employment of forces, although operational level logistics planning is generally remote enough from the hostilities to avoid characterization as direct participation.” 77

VI. Targetability of PMSCs

On the basis of the previous sections, the legal distinction for targeting PMSCs is the following: PMSC staff can be targeted when they qualify as combatants according to Article 4A(1) and (2) of the Third Geneva Convention and Article 43 of the Additional Protocol I, when they are members of an organized armed group, and when they directly participate in hostilities. PMSC staff are not targetable when they work for a non-state entity other than an organized armed group, when they defend others without

72 Id., pp. 544–545. Back
73 Id. Back
74 Sassòli, supra note 27, p. 551. Back
75 Schmitt, supra note 38, p. 545. Back
76 Id., pp. 542–543. Back
77 Id. Back


directly participating in hostilities (including defending military objectives against criminal activities), and when PMSC staff defend themselves. This applies both to staff of PMSCs without any particular status under IHL as well as civilians accompanying armed forces according to Article 4A(4) of the Third Geneva Convention and mercenaries in international armed conflicts, since all qualify as civilians for the purpose of targeting.

Whether or not a PMSC works for armed forces of a state party to an armed conflict can help determine the PMSC staff’s targetability. 78 If the PMSC does so, the contractor can be targeted unless the person is acting in self-defence or the defence of others against criminal actions, or unless the person’s actions are not part of a specific collective operation. Any such determination requires good information and analysis of what the PMSC personnel is doing and how this qualifies. If there remains doubt over the legal status of the PMSC staff, however, the person shall be considered a civilian that cannot be attacked. 79

Any attack on PMSC personnel needs to respect the principles of proportionality–as and where applicable–and the duty to take precautions. 80 Even when PMSC staff are not targetable, the nature of their services oftentimes requires them to operate in areas where hostilities are ongoing or likely to erupt. Moreover, their activities may put them close to armed forces and other military objectives. As a result, they are exposed to an increased risk of incidental death or injury due to attacks.

Because of their general support to war-related activities and their voluntary engagement, it is worth asking if PMSC staff count less than usual civilians in the assessment of lawful collateral damage. Regarding voluntary human shields, i.e. civilians that voluntarily position themselves around fighters to protect them from attacks by raising the collateral damage higher than the military advantage would justify, some argue that those voluntarily engaging in constituting a human shield should weigh less than usual civilians in the proportionality assessment. 81 This is a minority view, however. Moreover, this logic cannot be easily applied to PMSCs because voluntary participation as human shields specifically intends to undermine the application of the principle of distinction, whereas this is not the case for voluntarily engaging in private security activities. This could also open the Pandora’s box of classifying certain civilians’ lives as less important than others. 82 For conceptual but also practical clarity, PMSC staff qualifying as civilians shall be protected as such, unless directly participating in hostilities.

For attacks against PMSCs and when attacks on combatants or military objectives may also hit PMSC staff, the principle of precaution applies. Those planning and deciding an attack need to take all feasible measures to verify that the target is legitimate under IHL. Given the diverse roles and tasks of PMSCs, this requires solid intelligence and legal analysis to distinguish between PMSC staff that can be attacked and those that cannot. It is also necessary to take all feasible precautions in the choice of means and methods of warfare to avoid or minimize incidental loss of civilian life, such as choosing the time of attack and a tactic or weapons with an impact radius that spares PMSC staff. The attack must be suspended if it becomes obvious that the PMSC staff is not targetable. If a choice between military objectives having a similar military advantage is possible, the objective that may be expected to cause the least danger to PMSC staff must be selected.

Furthermore, those employing PMSCs must not put them in harm’s way according to Article 58 of the Additional Protocol I. Strictly speaking, this rule’s consequence is that only soldiers but not PMSC

78 For this distinction, it is important that the PMSC does not just work for any state but a state that is party to the armed conflict. Only in the latter case, the PMSC staff is targetable. PMSC staff protecting embassies of states that are not involved in an armed conflict, for instance, cannot be targeted. Back
79 API, Article 50(1). Back
80 API, Articles 51(5)(b); 57; 58. Back
81 Program on Humanitarian Policy and Conflict Research, Commentary on the HPCR Manual on International Law Applicable to Air and Missile Warfare (Cambridge, Harvard University, 2010), p. 144. Back
82 Y. Dinstein, for instance, suggests that medical personnel count for more than other civilians. On the other hand, he rejects the proposition that civilians working in munition factories, which in his view are legitimate military objectives, constitute “quasi-combatants” that do not count for the sake of the principle of proportionality. See: Y. Dinstein, The Conduct of Hostilities under the Law of International Armed Conflict (Cambridge, Cambridge University Press, 2004, 3rd ed.), p. 124. Back


personnel shall protect military personnel and materiel. States continue to outsource such protection services to PMSCs, however. In this case, to strengthen the protection against attacks of PMSC staff that only protects installations against non-conflict related actions, precautionary measures could be to clearly indicate this by their clothing, distinctive signs, and equipment, as well as to communicate the PMSCs’ responsibilities to adversaries. It is also necessary to inform PMSC staff on their risks and how to react in case of military attacks.

VII. Conclusion

The increasing use of PMSCs in situations of armed conflicts further contributes to the legal complexities of modern military operations. Knowing the legal status of PMSCs and their staff, and if they can be targeted, is not easy for planners, operators, and PMSC staff. The best way to bring legal clarity to the issue would be for states to formally integrate PMSCs into their armed forces. This is unrealistic, however, because states notably wish to outsource war-related tasks to ensure operational and contractual flexibility as well as to reduce direct costs related to the engagement of armed forces. Given the high risks that PMSC staff are oftentimes exposed to, a general recommendation to states is to avoid placing them in legally ambiguous situations where they can easily fall into the category of civilians directly participating in hostilities. Improving PMSC staff’s knowledge of their legal status and its consequences regarding their targetability through training is another way to avoid confusion and improve their safety.

States are likely to continue to use PMSCs for tasks that involve a high likelihood of being targeted or becoming collateral damage. Moreover, the complexities and dynamics of modern conflicts make it hard for PMSC staff to assess their legal situations. Thus, an increased responsibility for the PMSC staff’s safety rests with those who attack them or targets nearby. While certain PMSC staff are lawful targets, others are civilians and protected as such. Having clarity on their targetability should allow targeting states to better comply with their responsibilities under international law. Indeed, PMSC staff’s high risk of death or injury is an essential component of their business risk, which they accepted when entering into the contractual arrangement governing their activities. This, however, does not absolve parties to a conflict from their obligations under IHL.