The American people have spoken: Donald Trump won the presidential election in a landslide, securing himself a second term in the White House that is due to begin on January 20th next year. The Republican nominee’s resounding victory comes with major implications for the war in Ukraine: Shortly after the election, the Wall Street Journal reported that a peace plan that would allow Russia to keep the Ukrainian territory it currently occupies was circulating within Trump’s transition team.
Regardless of its political feasibility, this plan raises important legal questions: Does international law allow aggressor states to walk away with territorial gains after starting a war? And would a peace agreement along these lines affect the obligations of third parties? By answering these and other questions, this post seeks to shed light on some aspects of the jus post bellum that might emerge in Ukraine under the incoming Trump administration.
Trump’s purported proposal for peace
The Trump team’s leaked plan (hereinafter: “the proposal”) would allow Russia to maintain control over the roughly 20% of Ukrainian territory it currently occupies, including Crimea. The proposal does not specify whether Ukraine would be required to formally cede sovereignty over these territories to Russia. In addition, a demilitarized zone patrolled by non-U.S. third party forces would be established, and Ukraine would need to abandon its bid for NATO membership for at least twenty years. In exchange, Ukraine would continue to receive military aid from the U.S. to prevent Russia from launching another invasion.
It is important to note that Trump’s transition team has not yet confirmed the authenticity of the proposal. However, its content would be in line with some of the statements Trump made during his campaign: Heavily criticizing the Biden administration’s approach to the conflict, he promised to end the war within 24 hours if elected. In addition, he reportedly stated that he would pressure Kyiv to make territorial concessions to Russia in order to facilitate a settlement. Trump’s actions since becoming President-elect have arguably been more balanced: In a phone call that the Kremlin denies took place, he reportedly warned Russian President Putin not to escalate the war any further. What the next administration’s Ukraine policy will look like therefore remains largely a matter of speculation.
Nevertheless, the prospect of a U.S.-backed peace plan that would require Ukraine to give up territory remains on the table for now. Further analysis is therefore warranted.
An unequal treaty?
The main legal obstacle to any peace agreement requiring Ukraine to make concessions to Russia is Article 52 of the Vienna Convention on the Law of Treaties (VCLT), which reads:
“A treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the Charter of the United Nations.”
The provision makes clear that such treaties, referred to as “unequal” or “leonine” treaties during the VCLT’s drafting process (see YILC 1966, vol. II, pp. 17 et seq) are not merely voidable, but void ab initio. This principle is a relatively recent addition to the international law of treaties. It developed only after the end of World War II, following:
“The endorsement of the criminality of aggressive war in the Charters of the Allied Military Tribunals for the trial of the Axis war criminals, the clear-cut prohibition of the threat or use of force in Article 2(4) of the Charter of the United Nations, together with the practice of the United Nations itself” (Draft Articles on the Law of Treaties, 1966, Article 49, commentary 1).
Ukraine and Russia are both parties to the VCLT, as noted by the ICJ in its recent judgment on the merits in the ICSFT/CERD case, para. 46. Article 52 also reflects customary international law. Consequently, there is no doubt that the legal principle embodied in the provision is applicable between the two states.
The scant jurisprudence we have indicates that the threshold for proving that a treaty results from an illegal threat or use of force is a relatively high one (Fisheries Jurisdiction (UK v. Iceland), para. 24). In the case of Ukraine, however, even the most demanding standard of proof would easily be met: In March 2022, the U.N. General Assembly unequivocally denounced Russia’s “Special Military Operation” as an act of aggression contrary to Article 2(4) U.N. Charter. It is clear that Ukraine would never voluntarily allow Russia to take control of large swaths of its territory. Nor would it agree to give up its long-held aspirations to join NATO. Any agreement providing for such concessions would therefore fall under Article 52 VCLT, rendering it void. This result is unaffected by the fact that Russia’s initial plan was likely to conquer all of Ukraine, and that the implementation of the proposal could therefore be seen as the “lesser evil”: Even if an aggressor is only partially successful, the result remains the product of an illegal use of force (Schmalenbach in Dörr/Schmalenbach Commentary to the VCLT, 2nd edn. 2018, Article 52, para. 23).
Given that peace treaties are by definition preceded by the use of force, one might be inclined to think that Article 52 VCLT does not apply to them. However, there is nothing to back up such a teleological reduction: Acknowledging that the article represented a progressive development rather than a codification of pre-existing legal principles, the International Law Commission (ILC) stated that:
“The rule […] cannot therefore be properly understood as depriving of validity ab initio a peace treaty […] procured by coercion prior to the establishment of the modern law regarding the threat or use of force” (Draft Articles on the Law of Treaties, 1966, Article 49, commentary 7).
The Draft Articles thus envisaged that future peace treaties would indeed be void if they resulted from the threat or use of force. Simply put, the idea of a “victorious peace” dictated by those who prevail on the battlefield is not sanctioned by modern international law.
Consequences for third states?
Even if a peace treaty were to formally transfer sovereign title to Crimea and the occupied parts of the Luhansk, Donetsk, Kherson and Zaporizhzhia oblasts to Russia, this transfer would be void under Article 52 VCLT. Consequently, there would be no valid consent on the part of Ukraine for Russia to assume sovereignty over these territories. In the absence of such consent, Russia’s (illegal) annexation of the occupied Ukrainian territories could not subsequently become a (legal) cession.
As a consequence of the inability of an invalid peace treaty to “heal” the annexations, the obligations of other states in this regard would remain unchanged: Under the customary principle known as the Stimson Doctrine, which is now enshrined in Article 41(2) of the Articles on State Responsibility, third states must not recognize the effects of an annexation. The precise content of this duty was first spelled out by the ICJ in its 1971 Advisory Opinion on Namibia, and again this year in the Advisory Opinion on Israel’s policies in the Occupied Palestinian Territory. According to the Court, states are not only under an obligation to abstain from formally recognizing Russia’s sovereignty over the territories concerned; they also must prevent any trade and investment relations that would assist Russia in maintaining control over them (Occupied Palestinian Territory AO, para. 278). The EU already carries out this obligation by Council Regulations No. 692/2014 and No. 2022/263.
No way forward?
In summary: Any agreement that would require Ukraine to make concessions to Russia against its will cannot take the form of a legally binding treaty. Ukraine’s sovereignty is protected by Article 52 VCLT. With respect to the occupied territories, the customary duty not to recognize annexations provides an additional safeguard. The floated proposal could therefore only be implemented as a non-binding political agreement akin to the Joint Comprehensive Plan of Action (JCPOA), a.k.a. the “Iran nuclear deal”. Such an agreement would formally leave Ukraine’s sovereignty over the occupied territories untouched, thus leaving open the possibility of returning them to the control of the Ukrainian government eventually. The U.S. could join such a political agreement as a guarantor. In the meantime, the territories would remain subject to the law of belligerent occupation as enshrined in Articles 42 et seq. of the Hague Regulations and Articles 47 et seq. of the Fourth Geneva Convention.
A peace plan could also be enacted by the U.N. Security Council, which is not bound by Article 52 VCLT (Schmalenbach in Dörr/Schmalenbach Commentary to the VCLT, 2nd edn. 2018, Article 52, para. 39, 48-50). However, that would require the consent of all five permanent members of the Security Council, see Article 27(3) U.N. Charter. Not only the U.S. but also France and the UK have steadfastly supported Ukraine since the beginning of Russia’s full-scale invasion in 2022. Therefore, such a fundamental change in policy to the detriment of Ukraine seems rather unlikely – even with a Trump administration in the White House.
