UK Supreme Court Rules Against State Immunity in ICSID Enforcement

The UK Supreme Court has delivered a landmark ruling affirming that states party to the International Centre for Settlement of Investment Disputes (ICSID) Convention cannot invoke state immunity to resist the recognition and enforcement of ICSID arbitral awards within the United Kingdom. The unanimous decision, handed down on March 4, 2026, concerns appeals brought by the Kingdom of Spain and the Republic of Zimbabwe.

Background to the Appeals

The cases centered on whether Spain and Zimbabwe could utilize sovereign immunity, as outlined in section 1 of the State Immunity Act 1978 (SIA 1978), to prevent the registration of arbitration awards issued against them. The companies involved – Infrastructure Services Luxembourg S.À.R.L. And Energia Termosolar B.V. (against Spain), and Border Timbers Ltd (against Zimbabwe) – had successfully applied to the High Court of England and Wales to register the awards .

The Court’s Decision

The Supreme Court determined that by acceding to Article 54(1) of the ICSID Convention, both Spain and Zimbabwe implicitly submitted to the jurisdiction of the English courts for the purpose of recognizing and enforcing ICSID awards. This submission overrides the general state immunity provisions under section 2(2) of the SIA 1978, preventing them from relying on adjudicative immunity to oppose the registration of the awards.

Implications for Investor-State Dispute Settlement

This ruling is considered a significant development in the field of investor-state dispute settlement (ISDS). It reinforces the framework established by the ICSID Convention, which currently has 158 contracting states, for the recognition and enforcement of arbitral awards. The decision aligns with a growing international trend clarifying the relationship between state immunity and the enforcement of ICSID awards, with similar rulings emerging in jurisdictions such as Australia, Modern Zealand, Malaysia, the United States, and the British Virgin Islands.

Legal Representation

Border Timbers was represented by Dominic Kennelly and Catherine Drummond of 3VB, led by Christopher Harris KC at Gibson Dunn, and instructed by Baker McKenzie. Spain was represented by Cameron Miles of 3VB, led by Lucas Bastin KC of Essex Court Chambers, and instructed by Curtis, Mallet-Prevost, Colt & Mosle.

Key Takeaways

• States that have ratified the ICSID Convention cannot rely on state immunity to block the enforcement of ICSID awards in UK courts.
• Accession to the ICSID Convention is considered a submission to the jurisdiction of the English courts for enforcement purposes.
• The ruling strengthens the international framework for ISDS and provides clarity for investors seeking to enforce awards against states.