The Kingdom of Spain v Infrastructure Services Luxembourg S.À.R.L. and another

A state waives adjudicative immunity under a treaty where the treaty’s words, interpreted under public international law, clearly and unequivocally express consent to jurisdiction. Specific words such as “waiver” or “submission” are unnecessary. Consent may arise from what is necessarily inherent in, or follows from, the express terms.

Article 54(1) of the ICSID Convention obliges every contracting state to recognise and enforce an ICSID award as if it were a final domestic judgment. This reciprocal obligation necessarily submits each contracting state to the adjudicative jurisdiction required for recognition and enforcement. Article 55 preserves immunity only from execution. A state therefore cannot resist registration of an ICSID award on the ground of adjudicative immunity.

Spain and Zimbabwe sought to set aside High Court orders registering adverse ICSID arbitration awards under section 1 of the Arbitration (International Investment Disputes) Act 1966. Each claimed immunity from the adjudicative jurisdiction of the English courts under section 1(1) of the State Immunity Act 1978.

The respective Commercial Court judges dismissed the applications, although their reasoning differed. The Court of Appeal dismissed both appeals in [2024] EWCA Civ 1257, holding that article 54(1) of the ICSID Convention was a prior written agreement submitting contracting states to jurisdiction for the purposes of section 2(2) of the 1978 Act. It remitted Zimbabwe’s reserved non-immunity defences to the Commercial Court.

The central issue in the Supreme Court was whether agreement to article 54(1), properly interpreted, constituted a clear and unequivocal waiver of adjudicative immunity. The Court did not hear or determine whether the separate arbitration exception in section 9(1) applied.

1. The appeals were dismissed unanimously. Article 54(1) of the ICSID Convention constitutes a clear and unequivocal submission by each contracting state to the adjudicative jurisdiction of the courts of every other contracting state for proceedings recognising and enforcing ICSID awards. Spain and Zimbabwe could not oppose registration on grounds of state immunity: paras 118, 144.

2. Section 2(2) of the State Immunity Act 1978 does not require prescribed language or an explicit reference to waiver, submission or immunity. A treaty waiver must clearly and unequivocally express consent to jurisdiction. Its existence is determined by interpreting the treaty under public international law, principally articles 31 and 32 of the Vienna Convention on the Law of Treaties. Meaning includes what is necessarily inherent in, and what necessarily follows from, the express words: paras 45, 53–69.

3. Article 54(1) imposes reciprocal obligations of result. Every contracting state must recognise an authenticated ICSID award as binding and enforce its pecuniary obligations as if the award were a final judgment of its own courts. A state cannot agree that another contracting state shall achieve that result while maintaining an adjudicative immunity that would prevent it. The obligation therefore necessarily entails consent to the required exercise of jurisdiction: paras 81–95.

4. The Convention distinguishes recognition and enforcement from execution. Articles 54(1) and (2) govern the former stages, while article 54(3) subjects execution to domestic law and article 55 expressly preserves immunity from execution. Article 55 does not preserve immunity from the antecedent adjudicative process. The Court was concerned only with adjudicative immunity, not execution: paras 21, 83–89.

5. The context, object and purpose of the Convention reinforced that construction. Its closed scheme produces binding awards which domestic courts generally cannot review on the merits, jurisdictional grounds reserved to the ICSID machinery, or public-policy grounds. Reciprocal recognition and enforcement protect against sovereign risk and support mutual trust among contracting states. The travaux préparatoires confirmed that awards against investors and states were to receive equal recognition, subject only to domestic immunity from execution: paras 97–133.

6. The Court expressed no view on section 9(1) of the 1978 Act or the Court of Appeal’s conclusions concerning the existence of arbitration agreements. The remittal of Zimbabwe’s reserved non-immunity defences to the Commercial Court remained in force, without any view being expressed on their merits: paras 145–146.

1. United Kingdom Supreme Court: The appeals were dismissed unanimously. The Court upheld the conclusion that article 54(1) of the ICSID Convention displaced adjudicative immunity. Zimbabwe’s remittal for determination of reserved non-immunity defences remained in force: [2026] UKSC 9 .
2. Court of Appeal: The conjoined appeals were dismissed. Article 54(1) was held to constitute a prior written submission to jurisdiction under section 2(2) of the State Immunity Act 1978. Zimbabwe’s reserved non-immunity defences were remitted to the Commercial Court: [2024] EWCA Civ 1257 ; [2025] 2 WLR 621 .
3. Commercial Court—Spain: Fraser J dismissed Spain’s application to set aside registration, holding that the relevant exceptions to immunity applied: [2023] EWHC 1226 (Comm) ; [2024] 1 All ER 404; [2023] 2 Lloyd’s Rep 299.
4. Commercial Court—Zimbabwe: Dias J dismissed Zimbabwe’s application. She held that registration was administrative and did not engage adjudicative immunity, although she also addressed the asserted statutory exceptions: [2024] EWHC 58 (Comm) ; [2024] 1 WLR 3417 .