Gap-Filling in Investment Protection Treaties: Dual Nationality and Treaty Silence in UNCITRAL Arbitration – A Comment on Romero V. Ecuador

Key Takeaways

• Majority applied dominant nationality, denied jurisdiction
• Dissent argued silence requires explicit limitation
• UNCITRAL treaties lack uniform dual‑nationality rule
• French courts favor opt‑out interpretation of treaty silence
• Substantial connection test increasingly central to jurisdiction

Summary

Romero v. Ecuador, an ad hoc UNCITRAL arbitration, highlighted divergent approaches to treaty silence on dual nationals. The majority tribunal invoked the dominant and effective nationality doctrine to deny jurisdiction, while a dissenting arbitrator argued that, absent explicit treaty language, dual nationals should retain access. The case underscores a broader split between opt‑in and opt‑out interpretations across UNCITRAL‑based BITs and related judicial review in France. Recent jurisprudence shows no uniform standard, with similar disputes under the Spain‑Venezuela BIT and NAFTA yielding opposite outcomes.

Pulse Analysis

Treaty silence is a structural feature of investment agreements, forcing tribunals to decide whether gaps can be filled with customary international law or must remain untouched. In the context of UNCITRAL‑based BITs, the absence of a specific clause on dual nationals creates a jurisdictional fault line. Scholars argue that this gap‑filling dilemma reflects a tension between state sovereignty and investor protection, especially when the treaty’s protocol explicitly directs tribunals to apply general principles of international law. The Romero decision brings this tension to the fore, testing the limits of interpretive leeway granted by treaty drafters.

In Romero v. Ecuador, the majority leaned on the dominant and effective nationality doctrine, effectively treating silence as an opt‑in mechanism that permits external legal concepts to shape jurisdiction. The dissent countered that such supplementation oversteps the parties’ consent, advocating an opt‑out approach where only explicit language can restrict claimants. This split mirrors earlier rulings under the Spain‑Venezuela BIT and NAFTA, where tribunals have alternately embraced and rejected the doctrine. French appellate courts, which often review awards seated in Paris, have consistently warned against reading limitations into silent treaties, reinforcing the opt‑out perspective and adding another layer of judicial scrutiny.

The practical fallout for policymakers is clear: ambiguous treaty drafting invites divergent tribunal interpretations, increasing legal uncertainty for investors. To mitigate this risk, states are increasingly inserting explicit nationality clauses or clarifying the scope of protection for dual nationals. For investors, understanding the jurisdictional landscape now requires assessing not only treaty text but also the interpretive posture of the chosen dispute‑resolution forum and the seat’s jurisprudence. As UNCITRAL arbitration continues to grow, the Romero case may serve as a catalyst for more precise treaty language, fostering greater predictability in cross‑border investment disputes.