Supreme Court, D. R. vs Republic of Mauritius, Nr. C.22.0012.F, 6 April 2023
The case concerns a French-Mauritian dual national who initiated arbitral proceedings against Mauritius under the 1973 France–Mauritius Bilateral Investment Treaty (BIT), alleging several treaty breaches. In 2018, however, the arbitral tribunal, having its seat in Brussels, found it lacked jurisdiction on the grounds that dual nationals of the two State parties fall outside the BIT’s personal scope of application, even though the treaty does not expressly address this issue. The investor sought annulment of the award before the Brussels Tribunal of First Instance, yet without success.
Contrary to the claimant, the Supreme Court held that the contested judgment had relied on the 2010 BIT between France and Mauritius – which excludes dual nationals from its scope but had not yet entered into force – not to determine the scope of the 1973 Treaty, but rather as an element revealing the common intention of the States Parties, at least as of 2010.
The Supreme Court further accepted that the contested judgment could rightly consider the customary norm excluding diplomatic protection for dual nationals as a “relevant rule of international law applicable in the relations between the parties” in the sense of Article 31(3)(c) of the Vienna Convention on the Law of Treaties (VCLT) for purposes of interpreting the 1973 BIT. By contrast, the European Convention on Human Rights (ECHR) and its First Additional Protocol did not qualify as such, as Mauritius was not bound by these instruments.
With respect to the reliance on national legislation as a “supplementary means of interpretation” under Article 32 VCLT, the Supreme Court rejected that supplementary means can be used only when the interpretation pursuant to Article 31 VCLT leaves the matter ambiguous or results in an outcome that is manifestly absurd (as they can be used to confirm an interpretation pursuant to Article 31 VCLT). On the other hand, it held that the reference to “preparatory work” in Article 32 is merely illustrative and that other supplementary means of interpretation may also be considered.