Ukraine’s Involvement in Cross-Border Raids by Russian Paramilitary Groups: Illegal Use of Force and Intervention or Lawful Self-Defence?

On 22 May 2023, two Russian paramilitary groups – the Liberty of Russia Legion (LSR) and the Russian Volunteer Corps (RDK) – conducted a cross-border raid from Ukrainian territory into the Belgorod region of Russia. After briefly ‘liberating’ some border villages, the fighters were forced to retreat on to Ukrainian territory again. This was not the first such raid by these groups. In March 2023, the RDK had staged an incursion into Russia’s Bryansk region. Russia referred to the groups as ‘saboteurs’ and ‘terrorists’ and claimed that it had killed several of its fighters in a ‘counter-terrorism operation’.

Ukraine denied any involvement in these cross-border raids. A spokesperson for Ukraine’s military intelligence directorate stated that the incursion was carried out ‘exclusively by citizens of the Russian Federation’ who had acted ‘completely autonomously’ and that Ukraine did not coordinate with them. According to Article 8 of the International Law Commission’s Articles on State Responsibility (ASR), which is reflective of customary international law, the conduct of a ‘group of persons shall be considered an act of a State under international law if the … group of persons is in fact acting on the instructions of, or under the direction of control of, that State in carrying out the conduct.’ The spokesperson’s statement was probably intended to pre-empt any attribution of the cross-border raids by the Russian paramilitaries to Ukraine. This may be explained by the fact that the United States and the country’s other Western allies do not want Ukraine to escalate the conflict by attacking Russian territory – and especially not using Western weapons in those attacks.

As a victim of Russian aggression, Ukraine would be entitled to attack military targets on Russian territory and even temporarily occupy Russian territory in exercise of its inherent right to self-defence. It could do so either directly with its own armed forces or indirectly by using military or paramilitary groups under its direction or control. For political reasons, however, Ukraine chose to disown the cross-border raid. The raid itself thus does not constitute an act of Ukrainian self-defence. This raises the question of its legality under international law.

The two Russian paramilitary groups are based in and operate from Ukrainian territory. They were infiltrating Russia from their base in the north-eastern Ukrainian region of Sumy. In an interview on 24 May 2023, a commander of the RDK told reporters that Ukraine did not provide weapons but supported the corps with information, fuel, food and medicine, and also treated the wounded. He also declared that every decision outside Ukraine was their own. One of the proclaimed aims of the groups is the ‘overthrow of the ruling regime in Russia’. A spokesperson for the LSR stated that the incursion was ‘the first steps in the main objective of overthrowing Putin’s regime through armed force.’ A spokesperson for Ukraine’s military intelligence directorate confirmed that on Russian territory the groups acted ‘according to their ideas and goals.’

Even if Ukraine did not provide the two Russian paramilitary groups based in its territory with arms and ammunition, assistance to these groups would – in terms of the UN General Assembly’s Friendly Relations Declaration – violate the principle of the non-use of force in Article 2(4) of the Charter of the United Nations by ‘organizing or encouraging the organization of irregular forces or armed bands … for incursion into the territory of another State’ and by ‘instigating, assisting … acts of civil strife or terrorist acts in another State’ involving the use of force.

In addition, the support given by Ukraine to the military activities of the two Russian groups would constitute a clear breach of the principle of non-intervention. As the International Court of Justice stated in the Nicaragua case: ‘The Court considers that in international law, if one State, with a view to the coercion of another State, supports and assists armed bands in that State whose purpose is to overthrow the government of that State, that amounts to an intervention by the one State in the internal affairs of the other, whether or not the political objective of the State giving such support and assistance is equally far-reaching.’ (p. 124, para. 241).

Ukraine’s support for the Russian paramilitary groups and their cross-border raids on the face of it thus constitutes an internationally wrongful act. The question is whether the wrongfulness of the act is precluded by a circumstance precluding wrongfulness (Articles 21-26 ASR).

The wrongfulness of Ukraine’s support for the cross-border raids is not precluded as a countermeasure in response to Russia’s illegal aggression against the country. Apart from the fact that the procedural conditions relating to countermeasures (Article 52 ASR) were not fulfilled, countermeasures shall not affect the obligation to refrain from the threat or use of force as embodied in the Charter of the United Nations (Article 50 (1) (a) ASR). As seen above, the obligation of non-use of force includes the duty to refrain from encouraging the organization of armed bands for incursion into the territory of another State.

The other circumstances precluding wrongfulness, including the plea of necessity, also seem not to be applicable as the prohibition of the use of force is – in the words of the International Law Commission (p. 247, para.1) – a ‘conspicuous example of a rule of international law having the character of jus cogens.’ According to Article 26 ASR nothing precludes the wrongfulness of an act which is not in conformity with an obligation arising under a norm of jus cogens.

Ukraine’s support for the cross-border raids, however, could nevertheless be lawful as an exercise of the inherent right of self-defence. According to Article 21 ASR, the ‘wrongfulness of an act of State is precluded if the act constitutes a lawful measure of self-defence in conformity with the Charter of the United Nations.’ The relevant ‘act of State’ is not the actual cross-border raid itself because, according to the statements of the actors involved, it is not attributable to Ukraine. Rather, the relevant act is Ukraine’s assistance to the Russian fighters carrying out that raid.

While assisting the incursion into the territory of another State by armed bands generally amounts to a violation of the principle of the non-use of force in Article 2(4) of the United Nations Charter, this is not the case if the assistance qualifies as self-defence. As the International Law Commission (p. 74, para. 1) pointed out, ‘a State exercising its inherent right of self-defence as referred to in Article 51 of the Charter is not, even potentially, in breach of Article 2, paragraph 4.’ There is no question of Ukraine exercising its right to self-defence against Russian aggression. The fact that Ukraine did not adopt the raid itself as an act of Ukrainian self-defence does not preclude it from relying on its right to self-defence with regard to other acts connected to the raid.

While self-defence, strictly speaking, does not operate as a justification with regard to violations of the principle of the non-use of force in Article 2(4) of the Charter, it may justify non-performance of other obligations that are related to the breach of that provision. As pointed out by Special Rapporteur James Crawford in his Second Report on State Responsibility (p. 34, para. 297), ‘in the course of self-defence, a State may violate other obligations towards the aggressor. For example, it may trespass on its territory, interfere in its internal affairs, disrupt its trade contrary to the provisions of a commercial treaty, etc.’ To the extent that Ukraine’s support of the Russian opposition groups also constitutes a breach of the principle of non-intervention, this would be covered by the justification of self-defence.

However, any measure of self-defence must be necessary and proportionate. Lawful self-defence is limited to measures warding off the attack. The principle of necessity and proportionality must be applied with regard to the actual measure taken; that is the provision of assistance to Russian paramilitary groups carrying out a cross-border raid. The ultimate goal of the groups – the overthrow of the Russian government – is of no relevance in this respect. While the latter may not be necessary to defend Ukraine against the Russian aggression, the cross-border raids serve a legitimate purpose of self-defence by pulling Russian troops away from key battlegrounds in Ukraine, tying down Russian forces and disrupting supply lines. Assisting the Russian groups thus corresponds to a necessity of self-defence.

While politically it may not have been opportune to endorse these cross-border raids by Russian paramilitary groups as acts of Ukrainian self-defence, legally the assistance provided to these groups is covered by Ukraine’s inherent right to self-defence. In the exercise of that right, Ukraine may literally carry the war to Russia, either by using its own troops or by taking advantage of Russian armed opposition forces.

Photo: ‘”Caesar”, the spokesperson and deputy commander of the Legion in an interview’ (24 May 2023, CC-BY-4.0)