The 2022 war in Ukraine has seen the enlistment of volunteers from all corners of Europe (and far beyond) on a scale unprecedented since the Spanish Civil War of the 1930s [1]. Almost 20,000 foreign volunteers had answered the initial call by President Zelensky to come and defend Ukraine less than two weeks into the invasion [2]. By many volunteers’ own accounts, they didn’t have to think twice, drawn by a strong moral obligation to assist. Although little detail has been shared publicly of there whereabouts since, media articles have begun to emerge suggesting that some may have been captured. Experienced veterans will be aware of the risks involved and that, if forced to surrender and interned, their status as lawful combatants is, at best, a grey area that could mean the absence of any basic rights or assurances of fair treatment from a legal standpoint.

What constitutes a lawful vs. an unlawful combatant and what are the implications in practical terms? A look at some current and recent examples in a European context addresses some common misconceptions and demonstrates why the matter is subject to such debate.

Article 4 of the Geneva Convention III (GCIII) sets out rules for special rights and protections for various types of combatants in an armed conflict based on their legitimacy. By now, 196 states have signed up to the Geneva Conventions I-IV (GCI-IV) and are therefore bound by them; which is every sovereign nation. However, far fewer nations have signed or ratified the Additional Protocols I-III (API-III).

Besides the official armed forces of any state, persons engaged in a conflict can be described by any number of terms (often non-exclusive); volunteers, legionnaires, mercenaries, private military contractors (PMCs), insurgents, terrorists, belligerents, guerrilla/resistance fighters etc. With their connotations, one party’s freedom fighters can be the opposing party’s terrorists. Similarly, there is frequent debate between the classification of foreign volunteers vs. mercenaries.

What Constitutes a Mercenary?

The term mercenary appears in many-a-vilifying media sensationalist headline, but more often than not, the term is misused. The International Convention against the Recruitment, Use, Financing and Training of Mercenaries (2001), a.k.a. the United Nations Mercenary Convention, deems mercenaries unlawful. Although, of the 46 ratifying states, major powers are notably absent. Nor have all major powers elected to ratify or have revoked their ratification (i.e. Russia) of the Additional Protocol I (API) of the Geneva Conventions addressing mercenaries and their lack of entitlement to being prisoners of war (POWs). Nations do adopt their own domestic laws criminalising mercenary activity but enforcement is often inconsistent and selectively applied.

These international laws broadly in agree in their definition of mercenaries by a set of specific criteria (all of which must apply):

  • Engagement: Is recruited locally or abroad specifically to engage in armed conflict (and does so);
  • Nationality/Residency: Is a non-national, non-resident (of any party involved);
  • Affiliation: Is not a member of the armed forces (of any parties involved nor of other non-parties who have sent them on official duty);
  • Motivation: Is motivated to take part in hostilities by desire for private gain and is promised compensation (substantially) exceeding that of equivalent combatants within the same party’s armed forces.

Since all criteria must be met, the scope is highly specific and suitably fits the stereotypical mercenaries of the colonial or even the medieval era. One could argue that such international law has, at a minimum, forced would be mercenaries to legitimise themselves; be it through establishing contracts to integrate with regular armed forces or registering as regulated PMC entities.

In practice, mercenaries are defined, not in a Protocol sense, but rather by a duck test (if it looks like, swims like and quacks like…etc.). In particular, motivation being primarily material/monetary can be difficult to substantiate. It also leaves the obvious loophole whereby if a foreign-recruited fighting group fits the criteria but the individuals are underpaid vs. their counterparts in the regular armed forces, and are perhaps even contracted-in as expendable troops, then they would not fit the bill.

What is the difference between PMCs and mercenaries? PMCs are licensed companies offering services in security, protection, training, intelligence, reconnaissance, consulting, logistics support etc. They are theoretically subject to strict scrutinisation and regulation (both at a national and UN level). Yet, European PMCs have been accused or found to be involved in clandestine operations, interference and direct (and thereby unlawful) combat; be it Russia’s notorious Wagner Group (renowned for having direct links to Putin’s government and a questionable track record in various operations conducted around the globe [3]) or the UK’s Aegis Defence Services accused of inappropriate/unlawful conduct in Iraq. The Swiss government and the Red Cross have explicitly stated their concern and objection to the role and recruitment of PMCs in the form of the Montreux Document (2008).

Are mercenaries lawful combatants? No, as far as the relevant international law is applicable. It is clearly stipulated in Article 47 of API to the Geneva Conventions that A mercenary shall not have the right to be a combatant or a prisoner of war”.

Are mercenaries criminals by virtue of their classification? Not according to international humanitarian law (IHL). [5] However, it may well be outlawed by their home nations.

Why are mercenaries prohibited by international law? What is the fundamental issue with hiring experienced personnel at cost to bolster efforts on the battlefield, provided they adhere to the other rules of lawful conduct? IHL does not seek to balance the odds and is impartial to the outcome provided that the negative humanitarian effects of a conflict are reduced as far as reasonably possible. It exists to “protect persons who are not or are no longer participating in the hostilities” and “restrict the means and methods of warfare” [5]. It was the protective failures of past wars and conflicts that triggered the main treaties, laws and subsequent revisions. From the 1987 Commentary of API Article 47, it is explained that the Protocol was born out of a time of colonial rebellion within the African continent, in which the role of mercenaries was actively interfering in national liberation movements (e.g. the Congo Crisis). The fitness for purpose of the Geneva Conventions and legacy IHL born out of a different era with different humanitarian concerns and with more conventional warfare in mind is thus a topic of recurring debate. The supplementary commentary does go some way to communicate the essence and intent of the Conventions and Protocols beyond the wording and the context is of crucial importance. Therefore, it is inadvisable to attempt to interpret the wording in the absence of the context.

What Constitutes a Foreign Volunteer?

For simplicity, let it be assumed that a foreign volunteer has first been ruled out as a mercenary according to the aforementioned criteria. The Geneva Convention and Protocols provision for legitimate foreign participation in armed conflicts, but in order to make the distinction between a lawful vs. unlawful combatant, additional considerations have to be taken into account.

  • Organisation & Affiliation: Have they been recruited is an official capacity as part of the armed forces, contracted as an organised unit with clear command, and a disciplinary system to uphold the rules applicable to armed conflict?
  • Distinguishability: Do they distinguish themselves from the civilian population when preparing/engaging in an attack (except in specific exceptions) and carry arms openly? (Article 44 of API) – a requirement for any lawful combatant for the purposes of adequate protection for civilians.

Are foreign volunteers lawful combatants? Provided they meet the above criteria and there is no compelling evidence to suggest they are financially motivated, they could reasonably be deemed lawful combatants. Naturally, the opposing party may challenge this status. The Russian Defence Minister has already ruled out POW status for foreign volunteers in the case of the 2022 war in Ukraine [6]:

I wish to make an official statement that none of the mercenaries the West is sending to Ukraine to fight for the nationalist regime in Kiev can be considered as combatants in accordance with international humanitarian law or enjoy the status of prisoners of war.

An address by Igor Konashenkov Russian Defence Minister) on 03 March 2022

The alternative to being a combatant or mercenary (according to the Protocol terms of an international armed conflict (IAC)) is that volunteer fighters are instead classed as civilians taking part in hostilities, since no other classification exists (as per Article 50, API). Even terrorists (albeit debated) must fall into one of these categories, whilst not giving acts of terrorism impunity.

Is it a criminal offence to volunteer to fight in a foreign conflict? It varies according to national law. For example, the Foreign Enlistment Act 1870 exists to prevent British subjects from joining any foreign war efforts against any friendly state of the UK in an unofficial capacity. Germany’s Nationality Act (Section 28) goes further to threaten that any subjects participating in any foreign conflict without governmental consent will lose their citizenship. Switzerland (in spite of a rich history of exporting mercenaries and the Swiss Guard still in a 500+ year service in the Vatican) prohibits any of its citizens joining a foreign military in any capacity, be it in a combat or non-combat role. Yet, prosecution does not always occur. Naturally, there are consequences and court marshalling will await deserting military personnel for going AWOL to fight in a foreign conflict. Certain European states have been prompted to take a harder stance on citizens joining foreign conflicts, such as Kosovo (Law No. 05/L -002), due to concerns about the number of Kosovars who had gone to fight for Islamic State.

A serious risk to volunteers is uncertainty over their fate upon returning home. Many westerners have been shocked to find themselves convicted of criminal or even terrorist charges in their own countries for going to fight against Islamic State in the Middle East. In the context of Ukraine, government spokespersons throughout Europe were quick to assure (even encourage) their citizens who wished to volunteer that they would not be prosecuted for doing so; evidence that such laws are selectively applied. Depending on the cause, a nod may be as good as a wink to provide sufficient assurances regarding home policy. But the mixed messaging, backtracking and U-turns on the initial endorsement now propagating throughout western nations with a domino effect reminds us that nothing is assured and policy, power and public opinion can change at any time.

It is important to note the distinction made between an IAC and a non-international armed conflict (NAIC) e.g. civil wars; in that the status of combatant is not applicable in the latter scenario, neither is POW status applicable. Additional Protocol II (APII) to the Geneva Conventions make no reference to the term. What does that mean for foreign participants? They instead fall under a general category as persons who do not take a direct part or who have ceased to take part in hostilities and, as a minimum, must in all circumstances be treated humanely (Article 4 and also Article 3 of GCIII).

Putting the Criteria to the Test

Taking a few recent realistic examples of foreign volunteers in armed conflicts, the key arguments for their classification as mercenaries vs. lawful combatants vs. civilians are outlined. The issue of whether or not any international law is binding depends on the ratification status of the involved parties and, although not the focus here, comprehensive resources exist such as the Rule of Law in Armed Conflicts (RULAC) portal that list the applicable international law and whether the conflict is of an IAC or NAIC nature (and why it is not always straightforward to determine). Their formal status, if in doubt, would be determined by a competent tribunal of the detaining party.

ExampleMercenary, Lawful Combatant or Civilian?
A left-wing French volunteer with no prior military experience fighting for the Kurdish YPG as a self-proclaimed “revolutionary” in Northern Syria against Turkey (2018)As the conflict is of a non-international nature, the volunteer would most likely classed as a civilian engaging in hostilities and thus may face criminal charges if interned by Turkey (a non-signatory to GC APII & III), without any special/POW status granted. Turkey make little, if any, differentiation between the terrorist PKK and the linked YPG; therefore the volunteer could face terrorism charges.

It seems that France, thus far, has tended not to prosecute returning citizens who have fought with the YPG, but has instead put them on a watchlist [7]. Conversely, other European nations have punished and even imprisoned their own citizens for the same act for advancing a political or ideological cause.
Nepalese Gurkhas fighting for the British against Argentina in the Falklands War (1982)Gurkhas are not classed as mercenaries as that they provide a continuous and long-standing service to the British Forces in accordance with a prior national agreement made in the 1940s. Gurkhas have openly served the British Crown for much longer (nearly 200 years). High-profile court challenges have taken place disputing their rights to citizenship, equal pay and pension rights; not being on par with their British counterparts.
A Danish ‘radicalised’ Muslim joining the Islamic State in Iraq (2016)The arena is the Iraqi government fighting a NAIC of many fronts. As it is non-international (proxy belligerents do not affect this status), the volunteer would likely be classed as a civilian engaging in hostilities and, as with the YPG foreign volunteer case, may well face terrorist charges. With mass detentions, Iraq would most likely seek to repatriate non-Iraqis to their respective home countries for trial [8], while the home country (under public pressure) may be reluctant to accept them back.

While many-a-western nation would and have turned a blind eye to any volunteer who has gone of their own initiative to fight against ISIS, fighting on the side of ISIS almost certainly implies severe punishment, either when caught attempting to join, or upon return. Separate penal laws exist nationally and internationally in the cases of joining official terrorist organisations (e.g. Resolution 2178 (2014) of the UN Security Council).

Denmark has gained reputation of being among the more lenient, owed to its focus on rehabilitation programs [9].
Chechen ‘Kadyrovites’ fighting for Russia in the armed conflict against Ukraine (2022)A simple internet search in English will yield a host of articles containing Kadyrov’s mercenaries in the title. But are they mercenaries as per the Protocol? Let’s review each of the criteria (they need only fail on one point to be disqualified from mercenary status):

– Are they recruited specifically to engage in armed conflict? Contested: As Ramzan Kadyrov’s personal protection force, the organisation has existed in an official capacity for over a decade and have participated in previous international campaigns; most notably in Syria. However, Russia’s critics claim that the recruitment for new volunteers is on such a significant scale that it is essentially an entirely different group.
– Are they non-nationals/non-residents of either party involved? Fail: Chechens of the Chechen Republic are Russian citizens.
– Are they members of the armed forces of Russia or have they been sent on official duty? Fail: Although their integration as part of Russia’s regular armed forces is de jure, their role is very much Kremlin-endorsed.
– Are they motivated to take part in hostilities by desire for private gain and compensation (substantially) exceeding that of their counterparts? Contested: There are allegations of (slightly) higher salaries and sign-up bonuses that do give some merit to this argument [10]. Other theories suggest that allegiance to Kadyrov is gained through intimidation tactics, or point to nationalist drivers, i.e. the presence of non-Kadyrovite Chechens fighting on the side of Ukraine (albeit not to the same extent).

If they are not mercenaries then are they lawful combatants? Kadyrovites do distinguish themselves from the civilian population and have the semblance of an organised command structure. They should profess to have a proper disciplinary system and uphold the Geneva Conventions (by extension of Russia) but even with their granted POW status, if tried and found guilty of serious violations and war crimes against humanity they could face criminal prosecution under national or international law.

In conclusion, they may be militants with a cruel and brutal reputation and could be coined as many things; however, mercenary is a misused term in the sense of the Protocol. Still, Russia are no longer legally bound to the applicable GC API. It must still be upheld by Ukraine, but only if Russia were to accept and apply the same provisions.
Wagner Group deployment in Libya in support of General Khalifa Haftar’s regime (LNA) against the official government (2019)Russia’s Wagner Group, despite gaining the reputation of mercenaries are technically PMCs. They are not mercenaries in the sense of the Protocol in that they are Russian subjects; regardless of their motives or remuneration.

Are they lawful combatants? In the case of their intervention in Libya, an NAIC (civil war) with armed groups competing for governmental power, there is no applicable definition for lawful combatants. If taken prisoner, there would be no special status granted other than the minimum standard in accordance with IHL and international human rights law (IHRL) since they are technically not a party to the conflict.

Because of Russia’s incessant denial of any links and what they insist is a robust law to prevent mercenaries within the country, the Wagner Group are able to operate with relative impunity and the is Kremlin not formally held accountable; a dangerous loophole when the evidence of the group’s committed war crimes is mounting. [11]
Serbian volunteer fighting in Donetsk for Russia against Ukraine (2014)This is a complex scenario, particularly given the established facts now vs. at the time. The first challenge was proving Russia’s direct involvement in the east of Ukraine, which was fervently denied until recently. That would make the difference between it being deemed an IAC or not, and hence determine the protocols applicable.

Supposing the international nature of the conflict had been established, with both Russia and Ukraine as signatories to GC API (as both were at the time), the volunteer must be proven to be part of an organised unit linked to the Russian armed forces (Article 43 & 50 of GC API) to be deemed a combatant. They cannot operate on their own initiative or they may be categorised as a civilian (whereby they may or may not be afforded POW status as per Article 45 of GC API). They must also distinguish themselves as a legitimate target and bear arms openly so as not to forfeit their POW status and thus be exempted from certain prosecutions as civilians.

Serbia outlaws fighting in foreign armed conflicts and did sentence the majority of volunteers who went to Ukraine in 2014 [12].

Rights and Implications

By virtue of both IHL (applicable in all situations of armed conflict) and IHRL (applicable at all times) it is never lawful for anyone be subjected to torture or inhumane treatment when taken captive by the opposing party, including denial to a fair trial. Although privileges outlined in GCIII are very specific, right down to a quota on the number of letters to family permitted to be sent, there is typically not much difference in how POWs vs. non-POWs are treated by belligerents; not least of all because of the complicated nature of making that determination. During an armed conflict, a detaining party is not going to sit around a table and debate the specific circumstances and merits of each-and-every detainee each time a new individual is captured. It would also require far more than just a baseline understanding of international law. Hence, it is usually more prudent to treat them in the same collective sense. However, POWs (as combatants) are immune to prosecution for the act of partaking in hostilities (provided no grave breaches or war crimes were permitted, as these are prosecutable) and a right to repatriation. Therefore there is a simpler system in place for their release upon the cessation of hostilities, unless a prior prisoner swap has been agreed. With judicial processes, non-POWs could be detained for longer. Depending on their home nation’s appetite and stance on their actions, they may or may not attempt to intervene with diplomatic efforts or appeal for their extradition. Indeed they are not bound to do so.

Any volunteer willing to accept the risk of consequences in their home country may find some assurance in the fact that there is no circumstance where their most basic human rights can be lawfully violated. Yet the realist knows the grim realities of war and that rife violations go unevidenced and unpunished. So whilst there are mechanisms to secure their rights as lawful combatants and POWs in the event of capture, these are not always upheld, nor are they enforced or breaches investigated.

Enforcement & Violations

The United Nations Security Council ultimately has the authority to enforce the Geneva Conventions, but rarely exercises its authority to do so. It then falls to other regional, international and national efforts to pursue justice, and that can unfortunately be a long and futile road all too often.