Infrastructure Services Luxembourg S.A.R.L v The Kingdom of Spain [2026] UKSC 9
•March 4, 2026
0
Why It Matters
The decision confirms that treaty‑based waivers of immunity bind sovereign states, strengthening the predictability and reach of international investment arbitration awards in the UK and beyond.
Key Takeaways
- •UK Supreme Court affirms treaty waivers override state immunity claims
- •Article 54 of the Exit Convention deemed clear jurisdiction submission
- •Both Spain and Zimbabwe must register arbitration awards as final judgments
- •Section 9 of State Immunity Act deemed unnecessary after treaty interpretation
- •Decision reinforces enforceability of investment arbitration awards across jurisdictions
Summary
The United Kingdom Supreme Court delivered a unanimous judgment in Infrastructure Services Luxembourg S.A.R.L v the Kingdom of Spain, confirming that Spain and Zimbabwe cannot invoke state immunity to block the registration of arbitration awards under the 1966 Arbitration Act. The Court held that, by virtue of Article 54 of the 1965 Exit Convention, each contracting state has expressly consented to recognise and enforce awards as if they were final court judgments, satisfying the “prior written agreement” test in section 2(2) of the State Immunity Act.
The judgment examined the treaty’s wording, the Vienna Convention on the Law of Treaties, and the amounts at stake – €101 million against Spain and US$125 million plus interest against Zimbabwe. It clarified that a clear, unequivocal waiver of immunity does not require the word “waiver,” only that the treaty language necessarily leads to that conclusion. Consequently, the Court found no need to decide the applicability of section 9, which governs explicit arbitration agreements.
Lord Jones, joined by Lady Simler and other Law Lords, emphasized that the mutual obligations in Article 54 create a self‑contained enforcement scheme, distinguishing recognition from execution and preserving only execution‑related immunity. The judgment cited consistent international jurisprudence from Australia, New Zealand, Malaysia and the United States, reinforcing a global consensus that the Exit Convention waives adjudicative immunity.
The ruling solidifies the enforceability of investment‑related arbitration awards in UK courts, signalling to sovereign states that treaty‑based consent to arbitration overrides domestic immunity defenses. Investors gain greater certainty that awards will be recognised and enforced, while states must carefully draft treaty provisions to avoid unintended jurisdictional submissions.
Original Description
Infrastructure Services Luxembourg S.A.R.L and another (Respondents) v The Kingdom of Spain (Appellant);
Case ID: UKSC/2024/0155
Republic of Zimbabwe (Appellant) v Border Timbers Ltd and another (Respondents)
Case ID: UKSC/2024/0156
Judgment date: 4 March 2026
Neutral citation: [2026] UKSC 9
On appeal from [2024] EWCA Civ 1257
This case questions whether foreign states can rely on state immunity to set aside the registration of any ICSID arbitral award in the United Kingdom with which they do not consent to being enforced.
Two appeals have been grouped together on the basis that the appeals raise the same issues. Both arise from challenges to investment arbitration awards brought against States (Spain and Zimbabwe) by international investors in those countries, who claim they have suffered losses caused by the States in breach of their international obligations. Two arbitral awards found in favour of the respective investors, awarding compensation totalling €101m against Spain, and US$124m against Zimbabwe.
The First and Second Respondents subsequently applied to have their respective awards registered under the Arbitration (International Investment Disputes) Act 1966 (“1966 Act”), which gave effect to the United Kingdom’s obligations under the 1965 Convention on the Settlement of Investment Disputes between States and Nationals of Other States (“ICSID Convention”). These were duly registered. Once served, both Zimbabwe and Spain applied to have the registrations set aside by reason of State immunity. These applications were refused though for substantially different reasons.
The appeals by both States were subsequently grouped together before the Court of Appeal, who subsequently dismissed their application, on the grounds that both States’ agreement to the ICSID Convention was also an agreement that any ICSID arbitral award could be enforceable in a signatory State.
Both States now appeal this decision before the Supreme Court.
The issues are:
(1) Did the Court of Appeal err in law by finding that Article 54(1) of the ICSID Convention, properly interpreted, constitutes a submission to the jurisdiction by prior agreement for the purposes of section 2(2) State Immunity Act 1978 (“SIA”).
(2) (For the First Appellant only): Did Fraser J err in law by finding that there was a valid arbitration agreement between Spain and the First Respondents for the purposes of section 9(1) SIA, such that Spain was not immune from the adjudicative jurisdiction of the English courts pursuant to section 1(1) SIA.
The Supreme Court unanimously dismisses the appeals.
More information is available on our website:
0
Comments
Want to join the conversation?
Loading comments...