The Award in Rwanda versus the United Kingdom: The PCA’s Interpretation of VCLT, Article 13

The PCA’s Award in the arbitration between Rwanda and the United Kingdom, decided on May 15, 2026, was released on June 1, 20226. The arbitration related to the decision by the incoming Labour Government to cancel the Agreement between the United Kingdom and Rwanda (formally the Agreement between the Government of the Republic of Rwanda and the Government of the United Kingdom of Great Britain and Northern Ireland for the Provision of an Asylum Partnership to Strengthen Shared International Commitments on the Protection of Refugees and Migrants) to transport asylum seekers to central Africa (“the Asylum Partnership Agreement”).

The previous Conservative Government’s policy was highly controversial, with the legality of the decision to certify Rwanda as a safe-third country (even though the UK accepts refugees from Rwanda) and to send migrants and asylum seekers to Rwanda contested in British courts. Much about the domestic implications of the policy has been written elsewhere. The Award itself does not discuss them in any detail. Instead, from an international law perspective, the Award sheds important light on a little analyzed provision, namely Article 13, of the Vienna Convention on the Law of Treaties (“VCLT”). 

The Dispute between Rwanda and the UK

Prime Minister Sir Keir Starmer campaigned on a promise to terminate the Asylum Partnership Agreement with Rwanda. On Labour’s election, Rwanda sent a note verbale to the UK requesting clarification of the UK position (Award, para 64). The UK responded that it would not continue the removal of individuals to Rwanda and that it would “be considering the issue of formal termination of the treaty … in due course.” (para 65). Subsequently, on September 9, 2024, the UK engaged with Rwanda to discuss the termination of the agreement (para 67). Further meetings occurred between the parties in fall 2024. 

On November 13, 2024, the UK sent a note verbale to Rwanda, which concluded with the following words: “If the proposals set out above are acceptable to the Government of Rwanda, I have the honour to propose that this Note and your reply to that effect will place on record the understanding of our two Governments in this matter, which will come into effect on the date of your reply” (para 92). Rwanda replied on November 14, 2024 that “[t]he Minister of Foreign Affairs and International Cooperation has the further honor to confirm that the proposed arrangements are acceptable to the Government of the Republic of Rwanda.” (para 93). 

No significant further discussions occurred until February 2025, when the UK announced measures to be taken in response to Rwanda’s intervention in the conflict in the DRC, including the suspension of bilateral aid. Rwanda immediately condemned those measures and further stated that “the previous arrangements outlined in the aforementioned Note Verbale, dated 14 November 2024, are hereby rescinded. Rwanda and the UK remain bound by the arrangements as contained in the bilateral agreement for the Provision of an Asylum Partnership Agreement” (para 99). The UK responded that it considered that the parties had reached a binding agreement through the Notes Verbales (the “Supplementary Agreement”) that terminated those obligations. 

When other means of settlement failed, Rwanda filed its Notice of Arbitration on November 24, 2025, appointing Professor Mohamed Abdel Wahab as arbitrator pursuant to the Asylum Partnership Agreement. The UK appointed Judge Joan Donoghue. Judge Peter Tomka was appointed tribunal chairperson. 

Simplifying the facts for the purposes of this blog post, under the Asylum Partnership Agreement, the UK was to pay Rwanda 240 million pounds during the first year of the deal, 100 million during the second year, and 50 million each year during years three to five. It was to additionally pay 20,000 pounds for each relocated individual. Rwanda claimed, in addition to other ancillary relief, that those payments were still required as the Asylum Partnership Agreement had not been terminated. The UK, in response, argued that the parties had reached a valid Supplementary Agreement under which it was not required to make those payments.

The Question of Article 13, VCLT

The Tribunal found that, insofar as Rwanda and the UK are parties to the VCLT, the applicable law ruling over the Asylum Partnership Agreement was the VCLT. The central question in the arbitration was thus the status of the purported Supplementary Agreement reached through the 2024 Notes Verbales under Article 13, VCLT. 

Article 13 provides: “The consent of States to be bound by a treaty constituted by instruments exchanged between them is expressed by that exchange when: (a) the instruments provide that their exchange shall have that effect; or (b) it is otherwise established that those States were agreed that the exchange of instruments should have that effect.” Article 13 poses a unique problem for Tribunals. Its text was not included in the original text of the VCLT as proposed by the ILC. Instead, it was proposed by the Polish Representative to the United Nations Conference on the Law of Treaties, Mr. Nahlik, who argued that the draft articles did not cover all the methods whereby a state could express its consent to be bound.

References to Article 13 jurisprudence in the literature are extremely sparse. The Oxford Guide to Treaties contains only fleeting references to it. Prof. Van Assche, in his longer discussion of Article 13, identifies only five prior cases where the exchange of instruments between states has been litigated. In two such cases, Rapporteur Huber found that the exchange of letters between governments constituted an international agreement (Residence at Rio Martin Arbitration and British Possessions in Spanish Morocco). In Customs Regime between Germany and Austria (Protocol of March 19th, 1931), the PCIJ found that: “it is well known that … [international] engagements may be taken in the form of … exchanges of notes.” In two ICJ cases, the court addressed the effects of the exchange of letters. In Maritime Delimitation and Territorial Questions between Qatar and Bahrain, the ICJ decided, without references to Article 13, that exchanges of letters between Saudi Arabia and Qatar and between Saudi Arabia and Bahrain constituted international agreements. In Obligation to Negotiate Access to the Pacific Ocean (Bolivia v Chile), the ICJ, while recognizing the customary character of Article 13, declined to find that the exchange of notes recorded an agreement between the states involved.

Despite the paucity of jurisprudence, Van Assche has suggested that treaties concluded through the exchange of instruments constitute between 25 and 50% of all treaties. In other words, the meaning of Article 13 has the potential to bear on the interpretation of a great number of international agreements.

Article 13(a) Validity

Scholarly commentary suggests that instruments do not need to take any particular form under Article 13. That informality presents particular problems, as it may require the court or tribunal to interpret what exactly was agreed to if there is no authoritative version of a text, or if it is unclear if consent was actually given. 

Rwanda argued that for an exchange of notes to be valid under Article 13(a), three requirements must be met: there must be a statement that the proposal is acceptable or agreeable, the notes must place on the record a joint understanding or agreement, and the language used put the agreement into force (para 117). Rwanda argued that its language did not indicate a clear consent to be bound. It argued that the inclusion of the details of the Supplementary Agreement in a Technical Annex (para 120) and its particular use of language suggested that Rwanda merely believed that the language was capable of being accepted in future form, rather than actually being accepted (para 121). 

Conversely, the UK argued that Rwanda’s use of the term “acceptable” in its correspondence clearly indicated its clear agreement to forgo future payments as part of a provisional agreement to terminate the Asylum Partnership Agreement. The UK further argued that Rwanda’s specific language in its note verbale of February 25, 2025, indicated that it had intended to be bound by the November exchange of letters. The language in its note of February 25. 2025, where Rwanda informed the UK that the proposed Supplementary Agreement to forgo any additional payments under the ETIF was “hereby rescinded,” indicated that Rwanda viewed the previous exchange of notes as binding (para 156). 

Ultimately, the Tribunal found that the Supplementary Agreement was not a binding agreement under Article 13(a). It found that the Technical Annex to the Note verbale, sent on 13 November 2024 by the UK High Commission, along with Rwanda’s reply, on 14 November 2024 neither had the effect of placing the understanding of the two governments on the record nor provided the date of entry into force of the agreement (para 175). In other words, the exchanges of notes were insufficient with respect to exactly what was agreed to and the date such an agreement would enter into force. 

Article 13(b) Validity

That finding did not exhaust the Tribunal’ analysis. Turning to Article 13(b), it noted that under the VCLT, “the Parties’ intention to be bound can be established ‘otherwise’” (para 176). Neither party made extensive submissions on the meaning of Article 13(b). Rwanda, in its limited submissions, argued that “the bar for Article 13(b) [wa]s unquestionably very high” (para 117). In its submissions, the UK argued that, in considering validity under Article 13(b) of the VCLT, tribunals must consider “the text, the circumstances in which it had been drawn up and subsequent conduct” (para 146).

Reviewing the history of negotiations between the parties, including discussions in October 2024 prior to the November 2024 exchange of notes, the Tribunal found that an understanding was reached between the UK and Rwanda about how to address the UK’s request, and the legal consequences of the UK’s note verbale (para 182). It found that the parties did not express any reservations or limitations in those conversations. Rwanda simply informed the UK that “the proposed arrangements are acceptable.” On the majority’s view, the exchanges cumulatively constituted an agreement pursuant to Article 13(b) (para 196).

Dissenting and Separate Opinion

Professor Wahab, in his opinion, agreed that the Article 13(a) test was not met. On his view, Rwanda “neither confirm[ed] that such exchange validly sets out the common understanding of both Parties, nor did it mention a date of effectiveness” (Dissenting and Separate Opinion, para 26). However, he parted ways with the majority, finding that: “neither the exchanges or communications between the Parties prior to Rwanda’s note verbale of 25 February 2025, nor Rwanda’s reference to rescission … represent consistent or clear subsequent actions by the Parties showing consent to be bound” under Article 13(b) (para 111). 

The dispute between the majority and the dissent turned on how to understand Rwanda’s statements. Prof. Wahab found that Rwanda had made deliberate changes to the language proposed by the UK to avoid incurring binding obligations. For instance, during the early exchange of notes in fall 2024, Rwanda replaced the words “hereby agreed” with “respectfully requests” and recast the phrase “[t]his diplomatic agreement is underpinned” as “[t]his request is supported by” (para 92). In his view, Rwanda’s edits were “not merely cosmetic” and “cannot be construed as an acceptance of an offer” (para 93). 

Legal Principles as Established by the Tribunal

The decision should provide clarity as to the meaning of Article 13(a). The majority and the dissent, in ruling in favour of Rwanda, accepted Rwanda’s formulation of the three-part test for consent to be bound under Article 13(a): (1) “language that the proposals are ‘acceptable’ or ‘agreeable’,” (2) “language that the two notes constitute or place on record a joint understanding or agreement.” and “language as to entry into force or effect” (para 117). 

Unfortunately, neither the majority nor the dissent could provide a clear test under Article 13(b). On the view of the dissent, Article 13(b) was designed to address questions of extrinsic proof (para 16). According to that view, the use of extrinsic evidence necessarily imposed a high burden of proof: “the standard is … exacting: clear and convincing evidence of the parties’ intention at the time of the exchange is required … consistent actions by both States demonstrating a manifest intention to be bound are essential” (para 19). Conversely, the majority endorsed a multi-factorial analysis (and possible a lower burden of proof): “in considering this issue, it is necessary to take into account the circumstances relating to the exchange of notes, in particular the discussions between the Parties and the exchanges of various drafts in the preparation of which both of them were actively involved, as well as their subsequent conduct” (para 176). In this respect, the test for intent to be bound under Article 13(b) will need to be determined in future litigation.