Diverging paths? English courts restrict assignment of ICSID awards in contrast to other major enforcement venues

On 10 November 2025, the England & Wales High Court delivered an important decision in OperaFund Eco-Invest and Schwab Holding v. Spain, holding that an ICSID award rendered under the Energy Charter Treaty (ECT) cannot be assigned to a third party. 

These novel findings on assignability may potentially add another layer of complexity to enforcement efforts of ICSID awards in England – a jurisdiction which had shown itself amenable to ICSID enforcement actions, including against Spain – as well as to the secondary market for investment arbitration awards. 

Background

The case arose from one of numerous ICSID arbitrations initiated by investors in Spain’s renewable energy sector following detrimental changes to the country’s electricity remuneration scheme in the early 2010s. In 2019, an ICSID ECT tribunal awarded about EUR 30 million to the claimants. The award was later upheld in annulment proceedings, and the claimants subsequently sought to enforce it in several jurisdictions, including the United Kingdom and Switzerland.

The original award creditors then assigned their rights under the award to an investment fund called Blasket Renewable Investments LLC, who sought to step into their place in the English enforcement proceedings. Spain objected to the assignment, arguing that awards cannot be assigned under the ICSID Convention.

At the same time, Spain sought to set aside the original registration of the award on grounds of sovereign immunity. The High Court did not rule on this point, as Spain’s objection has been stayed pending the UK Supreme Court’s decision on the intra-EU question in Antin v Spain (expected in the first half of 2026).

Key legal issues in the judgment

Issue estoppel based on Australian ruling

Blasket’s primary submission was that Spain was estopped from disputing the assignment of the award because the Federal Court of Australia had already turned aside a similar objection in an August 2025 decision enforcing another ICSID award against Spain (see here our update on the Australian decision). 

The High Court rejected this argument. In the Court’s opinion, for issue estoppel to arise from a foreign judgment, the overseas judgment must be entitled to recognition, the same parties must be involved, and the issue must be identical in both proceedings. The High Court found that the Australian judgment remained subject to an unsealed order and an announced appeal, so it was not final, and therefore not entitled to recognition in the UK. 

Assignability of ICSID and ECT awards

Turning to the substance, the High Court noted that the ICSID Convention and the ECT contain no express provision either permitting or prohibiting assignment of awards rendered in investor-State disputes rendered pursuant to either Convention. 

The Court’s analysis therefore centred on Article 54 of the ICSID Convention, which governs States’ obligations to recognize ICSID awards. It concluded that, when read in context, the reference in Article 54 to “a party” seeking recognition or enforcement must be interpreted restrictively to refer only to the parties to the original arbitration, consistent with Article 53’s rule that an award binds only those parties. 

While acknowledging that the ICSID Convention elsewhere uses the phrase “party to a dispute,” the Court treated the two expressions as interchangeable. It considered immaterial that this interpretation might render the words “to a dispute” superfluous, finding that the Vienna Convention on the Law of Treaties does not require avoiding surplusage.

From a practical perspective, the Court opined that its findings do not go against commercial reasonableness given that Blasket could still recover sums under the assignment agreement as long as the original party to the arbitration is the one enforcing the award before English courts.

The High Court also found that the underlying award is unassignable under the terms of the ECT. The Court highlighted Article 15 (“Subrogation”), which governs situations where the State or a State agency indemnifies an investor and automatically acquires the investor’s claims. According to the Court, such provision would be unnecessary if assignment of ECT awards were generally permitted.

Finally, the Court also dismissed Blasket’s argument that the absence of an express prohibition should imply permission to assign. Considering customary international law, the Court did not identify a rule supporting such proposition. Notably, the Court stated that the answer to the assignment issue must come from treaty interpretation rules under the Vienna Convention, highlighting that the drafters of the ICSID Convention probably did not intend this issue to be left to domestic law – being the approach that (by contrast) has been followed by courts in the United States.

Assignability of rights arising from award registration under English law

Blasket argued in the alternative that even if the underlying award was not assignable, the registration of the award created new, independent rights capable of transfer under English law. The Court held that registration serves only a procedural function and does not change the nature of the rights recognized, nor create new substantive ones. 

Takeaways and outlook

In practical terms, the decision limits the ability of award assignees to pursue enforcement actions of ICSID awards before English courts in their own name. Importantly, however, the judgment does not affect the substantive enforceability of ICSID awards. Award creditors remain entitled to pursue enforcement, while third-party funders and assignees may still benefit commercially through private contractual arrangements. 

More broadly, the decision contrasts with recent developments in other jurisdictions, such as the U.S. District Court for the District of Columbia’s enforcement of assigned ICSID awards, highlighting divergent approaches across major enforcement venues. Stakeholders seeking to structure transactions and strategies involving ICSID arbitral awards will need to take these nuances into account.

The case is a timely reminder that, even within a similar enforcement landscape, different national courts may read the ICSID Convention in starkly different ways.  Given the outcome, it seems likely that the decision will be subject to appeal.