Writer: Carson Phillips
Editor: Cecelia Maillis
4/28/24
As of March 5th, leaked intelligence has confirmed that British troops are engaged in conflict in Ukraine. Other states including the US have provided Ukraine with funds and weaponry to support the war effort. Russia has claimed that any troops fighting alongside Ukrainian forces will be treated as “legitimate targets.” What types of supporting actions can constitute a third-party state as a legitimate target? Can Russia legally target Ukraine’s patrons under international law? Jus ad bellum, the law of neutrality, and international humanitarian law provide differing interpretations of these questions.
Under jus ad bellum, Ukraine is able to claim collective self-defense and ask other states to come to its aid. Collective self-defense includes providing weaponry and other means of support including intelligence and funds. While utilizing these supplies, Ukraine must abide by the jus ad bellum principles of proportionality, distinction, and precautionary measures - meaning Ukraine’s military actions should be proportionate to Russia’s, Ukraine should distinguish between Russian soldiers and civilians when striking, and should take all possible precautionary measures to avoid conflict. Obviously, none of these principles are likely to be violated on the part of Ukraine in the near future. States including the US have provided Ukraine with these reinforcements during the Russia-Ukraine war. Doing so does legally validate a use of force from Russia’s perspective, according to the precedent set in US v. Nicaragua (1986). The ICJ’s ruling in this case concluded that the US’s act of supplying a Nicaraguan-based rebel group with arms indicated that Nicaragua could legally take proportionate measures to combat the US’s efforts. This means that Russia would be able to act proportionately to counter Ukraine and its allies, though a proportionate response shouldn’t include any attacks beyond Ukraine’s borders, and these third-party supporting states would not be considered parties to the conflict according to the UN charter – so the US and Britain should not be considered military targets.
The law of neutrality provides a slightly different answer to the questions posed in this context. When a state supplies a warring state with funds, weapons, or intelligence, they are often considered to be violating the law of neutrality. Russia would be able to confront these violations of neutrality by means proportionate to these violations, given that they result from an illegal armed attack. An armed attack isn’t clearly defined in international law, but one could argue that these British troops are acting under the coalition of Ukraine and therefore do not represent a separate armed attack deriving from the UK. International humanitarian law provides a similar interpretation as jus ad bellum. It states that by simply providing Ukraine with weapons or similar provisions, a state is not considered a co-belligerent and therefore is not legally subject to Russian retaliation. Under IHL exclusively, Russia could theoretically target weapons that are being supplied to Ukraine before they reach Ukrainian soil (under the condition that it is absolutely certain the weapons were being distributed to Ukraine to harm Russia), however, doing so would be illegal under jus ad bellum (since it would require an armed attack to have occurred) and under the law of neutrality (because retaliation towards a third-party state is not valid when the neutral state provides only weapons).
It isn’t surprising that there isn’t a clear rule to cite when determining the implications of the UK’s decision to deploy British troops on the ground in Ukraine. The action can’t be clearly defined as an armed attack, and legal scholars believe that the UK’s actions can be interpreted as merely providing Ukraine with more resources to defend itself, which wouldn’t be enough to classify the UK as a co-belligerent. Of course, Russia will assert that the deployment of British troops can be considered an act of aggression, which authorizes retaliation. Until a third-party state acts on its own accord rather than acting through Ukraine, the ongoing conflict will likely remain between Russia and Ukraine.
References
Bluth, C. (2024, March 5). British troops operating on the ground in Ukraine – what
international law says. The Conversation. https://theconversation.com/british-troops-operating-on-the-ground-in-ukraine-what-international-law-says-224896
Jon Heller, K., & Trabucco, L. (2022). The Legality of Weapons Transfers to Ukraine Under
International Law. Journal of International Humanitarian Legal Studies, 1–24. https://doi.org/10.1163/18781527-bja10053
Schmitt, M. N. (2022, March 7). Providing Arms and Materiel to Ukraine: Neutrality, Co-
belligerency, and the Use of Force - Lieber Institute West Point. Lieber Institute West Point. https://lieber.westpoint.edu/ukraine-neutrality-co-belligerency-use-of-force/
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