In recent years, increasing global mobility has driven a rise in dual nationality cases in investment treaty arbitration, posing significant challenges to the investment treaty regime, which relies on the principle of nationality. This principle seeks to prevent individuals from bringing claims against their own State, thereby maintaining a clear distinction between foreign and domestic investors. The integration of dual nationals into this framework has prompted considerable debate and jurisprudential divergence.
Arbitral tribunals have encountered the complexities of reconciling dual nationality with treaty provisions, leading to the adoption of various interpretative and doctrinal approaches. These efforts reflect an ongoing evolution in the treatment of dual nationality within investment arbitration.
This note examines how these issues have been addressed in two notable cases involving Spain and its bilateral investment treaties (BITs) with Venezuela and Mexico, both of which involved claims brought by dual nationals.
Diamante Trading and others v. Venezuela
For instance, in the recent case of Diamante Trading and others v. Venezuela,[1] the tribunal upheld its jurisdiction over a claim brought by dual nationals under the Spain-Venezuela BIT.
The tribunal found that the Spain BIT did not preclude claims brought by dual nationals possessing the nationality of Venezuela as the respondent State, a position substantiated by the treaty’s negotiating history.[2]
The tribunal underscored that the claimants had submitted minutes from the initial round of BIT negotiations between Spain and Venezuela, revealing that the parties had discussed the potential inclusion of a residency requirement, with Venezuela referencing its BIT with Italy, which explicitly excluded claims by dual nationals.[3]
This evidence demonstrated that the contracting parties were fully aware of the option to expressly bar claims by dual nationals against one of their own States but ultimately chose not to include such a provision in the Spain–Venezuela BIT.[4] Furthermore, the claimants established that, at the time of negotiation, approximately 300,000 Spanish nationals resided in Venezuela – an element the parties could not have overlooked.[5]
The tribunal thus concluded that the absence of an explicit exclusion clause for dual nationals was a deliberate and informed decision.[6] This conclusion was further reinforced by the fact that both Spain and Venezuela had included such exclusions in other bilateral investment treaties.[7]
Significantly, the tribunal in its entirety found no justification for invoking the general rules of international law on diplomatic protection, reasoning that the Spain BIT functioned as lex specialis in this context.[8]
The tribunal observed that the relevance of diplomatic protection rules in the context of investor-State arbitration had been subject to academic and jurisprudential debate.[9] It further dismissed Venezuela’s reliance on the 1930 Convention on Certain Questions Relating to the Conflict of Nationality Laws, noting that the convention had limited international endorsement and predated significant legal developments in the field of investment arbitration.[10]
Moreover, Venezuela contended that under Article 31(3) of the Vienna Convention on the Law of Treaties (“VCLT”), other relevant rules of international law binding upon both parties to the BIT should be considered as part of the interpretative context.[11] Relying on this provision, along with the applicable law clause in the BIT, Venezuela attempted to incorporate general international law principles governing claims by dual nationals into the treaty’s framework.[12]
The tribunal rejected this position, holding that general international law could not override the specific terms negotiated by the parties within the treaty.[13] It reaffirmed that the ordinary meaning of the Spain-Venezuela BIT supported the admissibility of claims by dual nationals.[14] In alignment with the tribunal’s reasoning in Serafín García Armas,[15] the arbitrators concluded that the BIT operated as lex specialis, thereby taking precedence over customary international law.[16]
Antonio del Valle Ruiz et al. v. Kingdom of Spain
Another example presented a similar approach, likewise upholding the jurisdiction of the tribunal ratione personae over dual-national claimants in Antonio del Valle Ruiz et al. v. Kingdom of Spain.[17]
To begin with, the tribunal initiated its analysis with Article 31(1) of the VCLT, emphasising that treaty terms must be interpreted in their context.[18] According to Article I(5)(a) of the Spain BIT, an “investor” is a national of one Contracting Party bringing a claim against the “other” Party, implying a requirement of nationality diversity.[19] The BIT’s structure and objective, which focus on protecting investors of one State in relation to the other, reinforce this interpretation.[20]
The BIT, however, is silent on dual nationality. The tribunal rejected both parties’ positions – Claimants arguing for inclusion and Respondent for exclusion of dual nationals – based solely on the treaty text.[21] While the word “one” might be read narrowly to exclude dual nationals,[22] the tribunal declined this interpretation, noting language variations and context.[23]
The tribunal also dismissed the argument that ICSID jurisprudence, which excludes dual nationals, should apply to UNCITRAL arbitrations.[24] It affirmed that each arbitral forum operates under its own procedural rules and rejected a uniform interpretation of the term “investor” across all fora.[25] Since Mexico had not joined ICSID at the time the Parties signed the BIT, the tribunal deemed it unlikely that the treaty intended the exclusive application of the ICSID rules.[26]
In conclusion, it found that under Article 31(1) VCLT, the BIT does not explicitly address dual nationality, and thus, neither Party’s argument on this point prevailed.[27]
Further, the tribunal considered Article 31(3)(c) VCLT and invoked the principle of systemic integration, interpreting the treaty within the broader context of international law.[28] Where a treaty is silent, customary international law may fill the gap.[29] In the case of dual nationality, principles of diplomatic protection may be applied,[30] such as the principle of predominant nationality.[31]
To determine predominant nationality, several factors are considered, such as habitual residence,[32] centre of interests, family ties, public life participation, national attachment,[33] employment, financial interests, and indicators like taxation and social security.[34] None of these is conclusive, and their relevance depends on the context of each case.[35]
In the case in question, all relevant indicators pointed to Mexico: the dual nationals resided, paid taxes, and had family ties there.[36] The use of a Spanish passport, including by Mr. del Valle,[37] was immaterial, given the overwhelming connection to Mexico. Moreover, Spain did not present convincing evidence to suggest that Spanish nationality was predominant.[38]
Thus, the tribunal deemed Mexican nationality predominant for all eight dual nationals,[39] qualifying them as “investors” under Article I(5)(a) of the Treaty and affirming its jurisdiction ratione personae.[40]
Conclusion
The increasing prevalence of dual nationality cases has posed challenges to the traditional framework of investment treaty arbitration, which is fundamentally based on the principle of nationality. An analysis of recent tribunals’ reasoning reveals that establishing jurisdiction ratione personae over dual nationals requires a careful examination of treaty language, relevant customary international law, and the principle of systemic integration.
Notably, the decisions in Diamante Trading v. Venezuela and Antonio del Valle Ruiz v. Spain demonstrate a shift toward a more flexible, text-oriented interpretative approach. In both cases, the tribunals upheld jurisdiction over dual nationals, emphasising the importance of the treaty’s wording and broader interpretative context.
Although case law remains divided, these developments contribute to greater clarity in addressing dual nationality within the context of investor-State arbitration.
[1] Diamante Trading and others v. Venezuela, PCA Case No. 2019-49, Award, 27 May 2025.
[2] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[3] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[4] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[5] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[6] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[7] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[8] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[9] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[10] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[11] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[12] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[13] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[14] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[15] Serafin Garcia Armas and Karina Garcia Gruber, PCA Case No. 2013-3, Decision on Jurisdiction, 15 December 2014; L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[16] L. Bohmer, Revealed: arbitrators uphold jurisdiction over dual nationals but disagree on active act of investing requirement; respondent is ordered to pay damages for expropriation of food distribution venture, 5 June 2025, https://www.iareporter.com/articles/revealed-uncitral-tribunal-finds-that-spain-venezuela-bit-allows-claims-by-dual-nationals (last accessed 13 June 2025).
[17] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025).
[18] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [427].
[19] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [429].
[20] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [430].
[21] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [433].
[22] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [434].
[23] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [434].
[24] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [440].
[25] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [442], [444].
[26] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [445].
[27] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [446].
[28] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [448].
[29] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [450].
[30] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [461].
[31] Campbell McLachlan et al., International Investment Arbitration, Substantive Principles (2nd ed., Oxford University Press, 2017), paras 182-185.
[32] Nottebohm case (Liechtenstein v. Guatemala), 2nd phase, Judgment [1955] ICJ Reports 1955, 4, p. 22.
[33] Nottebohm case (Liechtenstein v. Guatemala), 2nd phase, Judgment [1955] ICJ Reports 1955, 4, p. 22.
[34] ILC Commentary on Diplomatic Protection 2006, UN Doc. A/RES/61/35 (2006), 61 UN GAOR Supp. (No. 49) at 505, Supp. No 10 (A/61/10) Art. 7, para 5.
[35] Nottebohm case (Liechtenstein v. Guatemala), 2nd phase, Judgment [1955] ICJ Reports 1955, 4, p. 22.
[36] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [482].
[37] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [482].
[38] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [482].
[39] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [483].
[40] Antonio del Valle Ruiz et al. v. Kingdom of Spain, PCA Case No. 2019-17, Award, 13 March 2023 (last accessed 13 June 2025), [483].