1. In a recent judgment, the English High Court held that an ICSID award against Spain could not be assigned by the award creditor to a third party.1 As a result, only the award creditor itself can seek registration and enforcement of an ICSID award in the United Kingdom.
2. This update summarizes the background to the OperaFund case and discusses its key findings and implications.
I. BACKGROUND
3. In 2019, OperaFund Eco-Invest Sicav plc and Schwab Holding AG (“Claimants”) prevailed in ICSID arbitration proceedings against the Kingdom of Spain, in one of numerous claims brought against Spain following its revocation of a solar energy framework designed to attract foreign investment. The tribunal found that Spain had breached the Energy Charter Treaty (“ECT”) and ordered Spain to pay the Claimants approximately €30 million.
4. The Claimants registered the ICSID award in the United Kingdom in 2021. Spain challenged the registration of the award based on, among other objections, state immunity, but the High Court provisionally upheld the registration pending the resolution of separate proceedings before the Court of Appeal involving Spain.
5. In 2024, the Claimants assigned the award to a fund named Blasket Renewable Investments LLC (“Blasket”). The Claimants then applied for Blasket to be substituted for the Claimants in the ongoing enforcement proceedings against Spain before the English courts. Under Civil Procedure Rule 19.2.4(a), “the court may order a new party to be substituted for an existing one if … (a) the existing party’s interest or liability has passed to the new party.”
6. Spain objected to the introduction of Blasket as a “new party,” arguing that under international law, an ICSID award may not be assigned. As a result, Spain argued that no “interest or liability” could have passed to Blasket under CPR 19.2.4(a).
7. The Claimants’ application to introduce Blasket into the English proceedings was decided by Judge Pelling KC in the High Court on 10 November 2025. In particular, as described below, he held that:
- Issue estoppel is not available against a state in respect of an issue decided in foreign proceedings where the state only appeared in those proceedings to contest jurisdiction.
- ICSID awards may not be assigned, and a purported assignee of an ICSID award may not seek its registration and enforcement in the United Kingdom. Further, regardless of whether ICSID awards are assignable, awards under the ECT are not.
- There is no rule of customary international law permitting or prohibiting assignment of an ICSID award.
- The registration of an ICSID award in the United Kingdom does not create additional domestic law rights that may be assigned to a third party to the dispute.
II. ISSUE ESTOPPEL IS NOT AVAILABLE AGAINST A STATE THAT HAS APPEARED IN FOREIGN PROCEEDINGS ONLY TO CONTEST JURISDICTION
8. Blasket had previously acquired additional ICSID awards against Spain from other award creditors. It then sought to register those awards in Australia. Spain challenged the registration, arguing that it was entitled to state immunity and that ICSID awards were not assignable. In August 2025, in four different cases, the Federal Court of Australia (“FCA”) rejected Spain’s objections and ruled that the relevant awards could be assigned to Blasket.
9. In the English court proceedings, the Claimants argued that Spain’s objection to the assignment of the award was precluded by issue estoppel following the FCA’s decision. There are three principal requirements for issue estoppel with respect to a foreign judgment:
- the judgment is entitled to recognition in the English courts;
- the parties in the two actions are the same; and
- the issue decided by the foreign court is the same as the issue in the English court.
10. While the latter two issues were not in dispute, Judge Pelling KC held that the Claimants failed to prove the first requirement: that the FCA judgments were entitled to recognition in the UK. The Claimants failed to prove this for two reasons.
11. First, for a judgment to be entitled to recognition in the English courts, it must be final and conclusive on the merits. The FCA judgments had not yet become final and binding in Australia. Spain still had time to challenge the judgments before they became final.2
12. Second, a foreign judgment can only be recognized against a judgment debtor in the English courts if the judgment debtor submitted to the jurisdiction of the foreign court.3 This rule also applies where the judgment debtor is a state.4 Spain only appeared in the Australian proceedings to contest the court’s jurisdiction on the basis of state immunity; Judge Pelling KC held this did not amount to submission to the jurisdiction of the Australian courts.5
13. As a result, the FCA judgments were not entitled to recognition in the English courts, and issue estoppel was not available to prevent Spain’s objection.
III. ASSIGNMENT OF AWARDS IS NOT PERMITTED BY THE ICSID CONVENTION OR THE ECT
14. Turning to the issue of whether the ICSID Convention permitted the assignment of awards to a third party, Judge Pelling KC first noted that the ICSID Convention does not expressly permit or prohibit assignment. He therefore resolved the issue using the principles of interpretation set out in Articles 31 and 32 of the Vienna Convention on the Law of Treaties 1969 (“Vienna Convention”) – that is, that a treaty must be interpreted in good faith according to the ordinary meaning of its terms in their context, and in light of the treaty’s object and purpose.6
15. A Contracting State’s obligation to recognize and enforce ICSID awards is contained in Part IV, Section 6 of the ICSID Convention. Within Section 6, Article 53(1) sets out that an award “shall be binding on the parties”; Article 54(2) then sets out that “a party” may seek the registration of an award in the territory of a Contracting State.
16. Reading these provisions in context, Judge Pelling KC considered it clear from the context that only the parties to the ICSID dispute are bound by the award, and only such parties may apply for registration of that award. As a result, he held that Article 54(2) does not permit a third party to the dispute to register an award.7
17. The Claimants and Blasket argued that such an approach would lead to “commercial absurdity” or “injustice” by preventing an assignee from exercising validly acquired rights. Judge Pelling KC disagreed, emphasizing that (1) the Claimants remained entitled to enforce the award against Spain; and (2) Blasket remained entitled to control the legal process and recover any sums recovered by the Claimants, as per the terms of the assignment agreement.8
18. Finally, Judge Pelling KC also briefly concluded that ECT awards are not assignable. Under Article 15 (Subrogation) of the ECT, where a state (or state agency) indemnifies an investor in respect of an investment in a host state, it will automatically acquire the investor’s claims against the host state. The host state must recognize this assignment. Judge Pelling KC agreed with Spain that Article 15 would be unnecessary if assignment was already permitted under the ECT.9
IV. ASSIGNMENT OF AWARDS IS NOT PERMITTED UNDER CUSTOMARY INTERNATIONAL LAW
19. Judge Pelling KC then examined relevant sources of customary international law, ultimately deciding that there is no established rule of customary international law that permits or prohibits assignment of rights under treaties such as the ICSID Convention.10
20. He acknowledged that, contrary to his conclusion, the courts of the United States have held that an ICSID award may be assigned.11 However, he argued that this approach was supported by principles of construction that are specific to the United States and not reflective of the approach required by the Vienna Convention. Judge Pelling KC emphasized that the Vienna Convention principles of interpretation, and not local law, should govern the question of whether ICSID awards may be assigned. Otherwise, the question would be decided in an inconsistent manner based on different local laws, which cannot have been the drafters’ intention.12
V. RIGHTS DERIVING FROM THE REGISTRATION OF AN ICSID AWARD IN THE UNITED KINGDOM ARE ALSO NOT ASSIGNABLE
21. Finally, the Claimants argued that even if the award itself could not be assigned, the award’s registration created new rights under English law that were capable of assignment.
22. Judge Pelling KC disagreed, holding that the Arbitration (International Investment Disputes) Act 1966, which implements the ICSID Convention in the United Kingdom, only facilitates enforcement and does not modify the scope of the ICSID Convention.13 In other words, “registration does not render assignable what is not assignable under the ICSID Convention.”14
VI. CONCLUSION
23. The High Court’s decision has a considerable impact on ICSID award creditors and assignees of ICSID awards in the United Kingdom. It removes an award creditor’s ability to cleanly transfer its interest to an assignee. Further, it leaves assignees reliant on the continued cooperation of the award creditor, who alone can register and enforce the award.
24. In light of the OperaFund decision, parties wishing to buy or sell ICSID awards may need to reconsider their existing or planned arrangements. Parties will still be able to transfer their interest in substance through private contractual arrangements, or through funding agreements, but the judgment is clear that only the award creditor itself may seek registration and enforcement of the ICSID award. As a result, it clearly complicates parties’ enforcement efforts.
25. The OperaFund decision also leads to diverging approaches between the United States and Australia, whose courts have permitted the registration and enforcement of assigned ICSID awards, and the United Kingdom. Considering that the ICSID framework has traditionally been appealing to commercial parties due to its consistency and predictability, this is arguably an unwelcome development. It remains to be seen whether Blasket will appeal the judgment and, if so, how the Court of Appeal will resolve the issue.15
