ICSID Convention Constitutes Submission to English Court Jurisdiction: UK Supreme Court Rules Foreign States Cannot Invoke State Immunity to Resist Registration of Awards

In <span class="news-text_italic-underline">Spain v Infrastructure Services Luxembourg Sarl [2026] UKSC 9</span>, handed down on 4 March 2026, the UK Supreme Court dismissed appeals by the Kingdom of Spain and the Republic of Zimbabwe against orders registering arbitral awards rendered under the International Centre for Settlement of Investment Disputs (“<span class="news-text_medium">ICSID</span>”) Convention as judgments of the High Court, pursuant to <span class="news-text_italic-underline">The Arbitration (International Investment Disputes) Act 1966</span>. The central question before the Court was whether the appellant states could invoke state immunity under section 1 of <span class="news-text_italic-underline">The State Immunity Act 1978</span> (“<span class="news-text_medium">SIA 1978</span>”) to set aside registration, or whether, by ratifying the ICSID Convention, they had submitted to the jurisdiction of the English courts by prior written agreement within the meaning of section 2(2) of the SIA 1978.

The Supreme Court held that waiver of immunity by treaty requires a clear and unequivocal expression of state consent, to be determined through treaty interpretation in accordance with Articles 31 and 32 of <span class="news-text_italic-underline">The Vienna Convention on the Law of Treaties</span>. The Court emphasised that such an expression of consent does not necessitate the use of explicit terms such as "waiver" or "submission". Meaning is to be derived from the words actually used and from what is necessarily inherent in and by what follows from the use of those words. The applicable test is whether the words used necessarily lead to the conclusion that the state has submitted to jurisdiction.

Applying that test, the Supreme Court held that Article 54(1) of the ICSID Convention constitutes a clear and unequivocal submission to the adjudicative jurisdiction of the English courts. The Court's reasoning proceeded on several grounds. By virtue of Article 54(1), each contracting state undertakes to recognise and enforce ICSID awards as though they were final judgments of its own domestic courts, whilst simultaneously consenting, on a reciprocal basis, to other contracting states doing likewise. This necessarily entails an express acceptance that, where an ICSID award is rendered against a contracting state, every other contracting state is obliged to exercise jurisdiction to recognise and enforce that award.

Such reciprocal obligations are fundamentally inconsistent with the maintenance of adjudicative immunity. The Court further noted that whilst Article 55 of the ICSID Convention preserves immunity from execution, it does not preserve adjudicative immunity. These conclusions were reinforced by the context, object and purpose of the ICSID Convention, the travaux préparatoires and a broad international consensus reflected in decisions from Australia, New Zealand, Malaysia and the US.

The decision is warmly welcomed as providing authoritative clarification from the Supreme Court on the relationship between the obligations created under the ICSID Convention and the state immunity enjoyed under English law.

<span class="news-text_medium">Case Reference:</span> <span class="news-text_italic-underline">Spain v Infrastructure Services Luxembourg Sarl [2026] UKSC 9</span> (4 March 2026)