When the going gets tough, politics tends to trump law, and words start to lose meaning. You can see it in the culture of sloppiness and misdirection that has developed around the use of terms like ‘terrorist’ and ‘combatant.’ These terms do have more-or-less precise meanings in international law, and there are good reasons for that precision, grounded in a deliberately established balance between liberty and security interests of individuals and states. But in popular parlance, and to the detriment of both liberty and security, these terms are used indiscriminately today.

Add to this list: “mercenary.” It also has a fairly precise meaning in international law, but it is often used loosely to describe people and conduct that may not meet the definition.  Take, for example, the role of United Arab Emirates (UAE) forces in Yemen. There are reports that the UAE, which is part of the Saudi-led coalition fighting Houthi rebels in Yemen, is using “mercenaries.” The reports are at once true and false. Each use of them term needs to be examined on its own.

The reports include allegations that a former senior Australian army officer has overseen the development of the UAE Presidential Guard, which plays a substantial role in the Yemen campaign. Does that make him a mercenary? No.

Other Australians are alleged to have trained and advised the UAE Presidential Guard in “leadership, training and mentoring roles.” Does that make them mercenaries? No.

British and French citizens, as well as other Australians and Colombians are alleged to have fought in the coalition in Yemen. Does that make them mercenaries? Very possibly, but more information is required. 

The international conventions that provide the legal definition for a mercenary were all negotiated during the waning days of 20th Century colonialism. They frown on fighting in someone else’s war for profit. Why? The answer is found in the (cumbersome) title of the U.N Human Rights Council Working Group that I now chair: “Working Group on the use of mercenaries as a means of violating human rights and impeding the exercise of the right of peoples to self-determination.” The link to self-determination is fairly obvious. We no more want foreigners fighting other peoples’ wars for profit and political domination than we want foreigners hacking or voting in our elections. Other reasons for concern are that mercenaries may not be subject to training or a chain of command that permit accountability for violations of human rights and humanitarian law.

The various definitions of mercenary do not, however, address training and advising someone else’s armed forces for profit. They also exclude those who are authorized or sent by their government to fight in someone else’s wars. That’s because if your government sends you, it is no longer someone else’s war – it becomes your government’s war and therefore, you’re not a mercenary. (Nationals of parties to the armed conflict are not mercenaries, no matter what their motive is to enter the fight).

To understand these distinctions, here is a quick look at how “mercenary” is defined in three international law treaties. The International Convention against the Recruitment, Use, Financing and Training of Mercenaries provides:

Article 1

For the purposes of the present Convention,

  1. A mercenary is any person who:

(a) Is specially recruited locally or abroad in order to fight in an armed conflict;

(b) Is motivated to take part in the hostilities essentially by the desire for private gain and, in fact, is promised, by or on behalf of a party to the conflict, material compensation substantially in excess of that promised or paid to combatants of similar rank and functions in the armed forces of that party;

(c) Is neither a national of a party to the conflict nor a resident of territory controlled by a party to the conflict;

(d) Is not a member of the armed forces of a party to the conflict; and

(e) Has not been sent by a State which is not a party to the conflict on official duty as a member of its armed forces.

  1. A mercenary is also any person who, in any other situation:

(a) Is specially recruited locally or abroad for the purpose of participating in a concerted act of violence aimed at:

(i) Overthrowing a Government or otherwise undermining the constitutional order of a State; or

(ii) Undermining the territorial integrity of a State;

(b) Is motivated to take part therein essentially by the desire for significant private gain and is prompted by the promise or payment of material compensation;

(c) Is neither a national nor a resident of the State against which such an act is directed;

(d) Has not been sent by a State on official duty; and

(e) Is not a member of the armed forces of the State on whose territory the act is undertaken.

Very similarly, the OAU Convention for the Elimination of Mercenarism in Africa provides:

A mercenary is any person who:

a) is specially recruited locally or abroad in order to fight in an armed conflicts;

b) does in fact take a direct part in the hostilities;

c) is motivated to take part in the hostilities essentially by the desire for private gain and in fact is promised by or on behalf of a party to the conflict material compensation;

d) is neither a national of a party to the conflict nor a resident of territory controlled by a party to the conflicts;

e) is not a member of the armed forces of a party to the conflict; and

f) is not sent by a state other than a party to the conflict on official mission as a member of the armed forces of the said state.

Both treaties require states party to criminalize mercenarism, but they are not widely ratified. See here and here. A third treaty, Additional Protocol I to the Geneva Conventions (AP I), Art. 47, defines mercenarism similarly to the OAU Convention and is widely ratified. But rather than criminalizing mercenarism, AP I merely declares mercenaries to be ineligible for combatant or prisoner of war status in international armed conflicts. (NB: unlike the International Convention, the OAU and AP I definitions require not merely recruitment to fight, but actual participation in hostilities.) See ICRC, Customary International Humanitarian Law, Rule 108 for further detail on the international regulatory framework applicable to mercenaries.

The criteria are cumulative meaning that all of them must be met for someone to be considered a mercenary under each treaty. A column on mercenaries is, therefore, not complete without mention of the adage that the definition is so detailed that anyone convicted of mercenarism should be shot, along with their lawyer.

Regardless of whether a state is party to any of these conventions, the implementation of criminal penalties for mercenarism is a matter for state law. In other words, states don’t need an international convention to prohibit mercenarism. On the other hand, not many states have domestic legislation outlawing it.

Colombia, Australia, France, the United Kingdom, UAE, Saudi Arabia and Yemen are all parties to AP I (which does not call for criminalization of mercenarism) but are not parties to either of the two mercenary treaties (which do). The United States is party to none of these three treaties. Apart from France, these countries also have no legislation to prohibit and punish their citizens who either advise parties to wars abroad, or fight in them. (Regulatory and sanction regimes and laws criminalizing material support for terrorist groups may, however, perform this function to a limited degree).

None of this means that mercenaries or other foreigners associated with the Saudi-led coalition are immune from legal liability. Saudi coalition forces operating in Yemen have been implicated in the commission of war crimes and perhaps even crimes against humanity (widespread or systematic attacks on civilian populations), stemming from what appears to be a pattern of either deliberate or indiscriminate targeting or disproportionate death and injury of civilians. Commanders of those forces, whether citizens of the coalition states or not, may be prosecuted if they order such attacks. In addition, commanders who merely know or should have known that forces under their command engage in such attacks and do nothing to prevent or punish them may be prosecuted under a theory of command responsibility, even if they have not ordered such attacks.  Quite separately, those who aid and abet such crimes, as has been alleged against the United States for providing intelligence and refueling services to the Saudi forces (see here and here) may also be criminally liable.

In some conflicts, private military and security companies (PMSCs) are hired not to attack, but only to protect combatants and military objectives from attack. Does that exclude their personnel from the definition of mercenary? Probably not. The law of armed conflict doesn’t discriminate between offensive and defensive use of force. Whether using force on offense, or merely defending an enemy’s military objective, PMSC personnel are directly participating in hostilities. They are targetable under the laws of war, and therefore likely to be considered “fighters” under the definition of mercenary. On the other hand, employees of a company contracted to provide services to military forces in an armed conflict are not, ipso facto, mercenaries. Think of food services on a military base or interrogation of detainees.

Individuals and businesses are not the only bearers of legal responsibility. States must not only respect the laws applicable in war, they must also ensure respect for them. See, ICRC Customary International Humanitarian Law, Rule 144. The obligation to ensure respect requires, at the very least, not providing support to parties to an armed conflict who systematically violate International Humanitarian Law (the law of armed conflict) provisions for the protection of civilians. At the most, it requires states to take measures short of the use of force (assuming force is not authorized by the Security Council), such as diplomacy or sanctions, in order to encourage the violating state to come into compliance with its international legal obligations. What relevance is this to the use of mercenaries? states that have committed to prohibit mercenarism should not aid and abet their use elsewhere by their companies or nationals. Likewise, even states that have made no such commitment should still not aid and abet the use of mercenaries in states that are party to either of the two Mercenary Conventions.

The more precise we are in applying terms like terrorist, combatant and mercenary, the more principled will be our application of law, and thus, the more likely that the application of law will serve the complementary interests of liberty and security.