Mercenary or Combatant? Ukraine’s International Legion of Territorial Defense under International Humanitarian Law

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On the fourth day after Russia’s February 24 armed attack and invasion of Ukraine, President Zelensky made a call for foreigners wishing to defend Ukraine to join the International Legion of Territorial Defense (ILTG), inviting individuals to contact foreign diplomatic missions of Ukraine in their respective countries (you could sign up here). Hundreds of American, Canadian, French, Croatian, Georgian and Belarusian fighters answered the call and traveled to Ukraine with or without their own governments’ approval. On Tuesday, March 1, Zelensky announced that approximately 16,000 foreign fighters have volunteered for military service.

In response, on March 3 Russia’s Defense Ministry spokesperson announced that none of the mercenaries detained the West is sending to Ukraine can be considered as combatants in accordance with international humanitarian law (IHL), or enjoy the status of prisoners of war (POW), and threatened to have them prosecuted as criminals for any subversive acts against the Russian army. 

Leaving aside the questions of military advantage or operational challenges that arise from having foreign fighters join the war in Ukraine, which have been addressed elsewhere, this post explores the legal classification and consequences for foreign fighters joining the ILTG and for the detaining state in light of IHL and their preliminary qualification by the Russian authorities. I argue that Russia could target these forces, but would violate IHL in treating these fighters as mercenaries, since they do not fulfill the criteria for a mercenary and are part of the armed forces of Ukraine. They should therefore be given POW status upon capture and not be prosecuted by Russia unless they commit war crimes.

Legal Criteria for Combatants and Mercenaries

The use of irregular foreign forces like mercenaries and foreign terrorist fighters (here, collectively,  “foreign fighters”), which straddle the blurry line distinguishing combatants and civilians under IHL, has intensified in recent armed conflicts. In addition to Ukraine, foreign fighters took part in the recent hostilities in Mali and Nagorno-Karabakh, in the Central African Republic since 2017, as well as in Syria and Libya. They might be members of terrorist groups like ISIS or Al-Qaeda, or private military companies like Russia’s Wagner Group, whose members are often referred to as Wagner mercenaries. The use of irregular forces raises practical questions for parties to the conflict with respect to their targeting and sanction upon capture.

For purposes of IHL, the classification and treatment of persons taking part in hostilities depends in large part on the classification of the armed conflict. That there is an ongoing international armed conflict with partial occupation in Ukraine is uncontroversial. Thus the Geneva Conventions, and the Additional Protocol I thereto, ratified by both Russia and Ukraine, apply.

As explained in a recent post on this blog, combatants falling within the definition of Article 4 of Geneva Convention III regulating the treatment of POWs, and the expanded definition of combatants provided for in Article 43 of Additional Protocol I, and are entitled to POW status and enjoy ‘combatant immunity’. That is, they are allowed to directly participate in hostilities and cannot be prosecuted for the mere participation in combat. The downside for combatants is that they could be targeted at any time by the opposing army’s armed forces, even while not participating in hostilities. 

Combatants are members of the armed forces of a party to the conflict or volunteers corps incorporated therein. According to the ICRC Commentary to Article 4, the requirement for membership in the armed forces, or the incorporation of the volunteer corps, is a matter of domestic regulation. But the incorporated unit must be a professional fighting force, fulfilling the criteria spelled out in Article 4A(2) of GC III, and be subordinate to the regular army command. The fact that an individual is a national of a third State and not a national of the armed forces in which they are serving is widely considered to be irrelevant when it comes to determining combatant or POW status. 

Mercenaries are professional fighters paid to intervene in an armed conflict in a country other than their own and are “motivated essentially by the desire for private gain.” The UN Working Group on Mercenaries has linked  them to interference with the right of peoples to self-determination, due to their involvement in the wars of national liberation on the African continent. Mercenaries have been banned by several treaties like the UN Mercenary Convention, which prohibits states from recruiting, using, financing and training mercenaries and requires them to criminalize mercenarism domestically. Both Russia and Ukraine have ratified this treaty and made being a mercenary a crime. 

The Geneva Conventions do not prohibit mercenarism as such, but provide that mercenaries do not have the right to combatant or POW status. They could therefore be prosecuted for merely participating in hostilities, as well as for the crime of mercenarism as such, by the detaining power.

A mercenary is defined very narrowly by Article 47 of Additional Protocol I to the GCs, as someone who: a) is specially recruited locally or abroad in order to fight in an armed conflict; b) does, in fact, take a direct part in the hostilities; c) is motivated to take part in the hostilities essentially for private gain, and is promised material compensation substantially in excess of that promised or paid to combatants of armed forces of the party hiring them; d) is neither a national or resident of the hiring state; e) is not a member of the armed forces of the hiring state; and e) has not been sent in an official capacity by a third state.

ICRC commentary to Article 47 provides that members of the armed forces of a party to the conflict who are not nationals of that party and who do not fulfill all six conditions of the definition of a mercenary are entitled to POW status.  According to the Commentary, it is sufficient for States which employ them to make them members of their armed forces for them no longer to be mercenaries.

Analysis of ILTG in Ukraine

The use of foreign fighters goes to the very beginning of the armed conflict in Ukraine in 2014, with both the Armed Forces of Ukraine (AFU) and so-called Donetsk and Luhansk People’s Republics resorting to them in the fighting in East Ukraine. This post only looks at foreign fighters joining the Ukrainian side.

With respect to the AFU, over 30 volunteer battalions were established under the auspices of the Ministry of Defense and the Ministry of the Interior, which citizens of Ukraine, foreign nationals and stateless persons joined. According to the Ukrainian authorities, as of 2015 up to 1,000 foreign fighters volunteered to join the armed conflict in Eastern Ukraine primarily for ideological reasons: to counter Russia’s aggression. The UN Working Group on Mercenaries has received no information on foreign fighters joining AFU solely for compensation, with some having to purchase equipment with their own funding or donations.

After a chaotic start to the armed conflict in Donbas, characterized at times by a lack of subordination of some volunteer battalions to the AFU, the Ukrainian authorities have regularized volunteer corps in domestic law and placed them under responsible command. On 17 March 2015, Law No. 2389 amended certain legislative acts to allow foreigners to join the AFU, on a contract basis, at the same level of remuneration as citizens of Ukraine of equal rank. In 2016, Presidential Decree No. 248 affirmed that “Foreigners, legally present on the territory of Ukraine, can be accepted for military service on contract with the Armed Forces of Ukraine on a voluntary basis.” The Decree stipulates that foreigners who pass a medical, psychological and professional competencies assessment become members of the AFU.

The Presidential Decree of 28 February 2022 No. 82 establishes a visa free regime for foreigners wishing to join the International Foreign Legion within the Territorial Defense Unit of the AFU, in line with the existing legal framework.

The Ukrainian authorities have obviously been well consulted by IHL specialists prior to the Zelensky call for volunteers. The formalization of members of the International Foreign Legion as members of the AFU brings them outside of the definition of mercenaries, as members of the armed forces of the state. While there is no clarity with respect to their compensation, Russian claims that the volunteers will be paid significantly more than their Ukrainian counterparts have not been verified.  Moreover, the fight against Russia’s aggression appears to be the prevalent motivation for fighters joining the ILTG, who are screened for their experience prior to engagement. Indeed, the recruitment website requires that recruits be “driven by a strong will to fight for peace.”


Members of the ILTG are thus combatants who would be entitled to POW status upon capture by Russia. Their prosecution and punishment for directly participating in hostilities, or for the crime of mercenarism, would be contrary to Articles 43 and 44 of API, and might amount to war crimes.

In matters of IHL theory often diverges from practice however. This is not the first time that Russia threatens to or mistreats POWs: in the first phase of the armed conflict, it has prosecuted Ukraine’s military pilot Nadiya Savchenko and the 24 Ukrainian sailors captured by Russia in November 2018, among others. All were subsequently released to Ukraine in a POW exchange. The tactic is obvious: it aims to deter foreigners who would be faced with the prospect of Russian prison from traveling to Ukraine.

But the prospect of penal prosecution in Russia, or the sending state which might prohibit individuals from joining foreign armed forces (one example is Belarus), has so far not deterred foreigners from coming in troves to defend democracy in Ukraine.

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