UK Supreme Court confirms no state immunity defence against recognition of ICSID awards in the UK

The Supreme Court has confirmed that States acceding to the International Centre for Settlement of Investment Disputes (ICSID) Convention also submit to the adjudicative jurisdiction of UK courts when recognising and enforcing ICSID awards. As a result, State parties cannot invoke state immunity to resist recognition of an ICSID award in UK court proceedings.

Background: the ICSID, the 1966 Act, and the SIA

The Kingdom of Spain v Infrastructure Services Luxembourg S.À.R.L & anr; Republic of Zimbabwe v Border Timbers Ltd & anr [2026] UKSC 9 (4 March 2026) was a joined appeal concerning two ICSID awards, one issued against Spain, and the other issued against Zimbabwe.

Both the High Court and the Court of Appeal had previously rejected applications by Spain and Zimbabwe to set aside recognition orders on state immunity grounds.

Under the SIA, a State is immune from the jurisdiction of UK courts, except in certain circumstances. One such exception, under section 2(2), is where the State has submitted to the jurisdiction of UK courts by prior written agreement.

The key issue addressed by the Supreme Court, therefore, was whether Spain and Zimbabwe had submitted to the jurisdiction of the UK courts for the purposes of section 2(2) of the State Immunity Act 1978 (‘the SIA’) by signing and acceding to the ICSID Convention.

The Supreme Court decision

The Supreme Court upheld the decisions reached by both the High Court and the Court of Appeal, holding that there was a waiver of state immunity with ICSID awards.

A treaty waiver must express a clear and unequivocal consent to the exercise of jurisdiction. The words ‘waiver’ or ‘submission’ are not necessary, and consent can instead be conveyed by what is necessarily inherent in the text. The test here is “whether the words used necessarily lead to the conclusion that the state has submitted to the jurisdiction”.

Relying on the principles of treaty interpretation set out in the Vienna Convention on the Law of Treaties, the Supreme Court concluded that Article 54(1) of the ICSID Convention constitutes a clear and unequivocal submission to jurisdiction, thus engaging the exception under section 2(2) of the SIA and displacing adjudicative immunity.

Practical implications

This decision is a welcome confirmation of the UK’s position, which is that recognition of ICSID awards in the UK cannot be resisted by States on state immunity grounds. It also marks a positive development for award creditors looking to enforce in the UK, as they will find that the recognition process now moves forwards more quickly.

That being said, translating an ICSID award into cash remains a two-step process of registering/ recognising the award and then executing against the assets. Whilst the Supreme Court’s judgment confirms that state immunity does not apply to the recognition phase, this decision does not affect any immunity a State may enjoy in the execution phase.

Under the SIA, States generally have immunity from execution against assets located in the UK to satisfy a court judgment or arbitration award unless the State has given prior written consent to execution, or if the property is used for commercial purposes.

Winning the arbitration is not always the end of the battle. Award creditors often need to locate assets against which to enforce, whether in the UK or elsewhere globally. In the case of arbitrations involving States, this will be complicated by State immunity against execution on their assets.

As such, investors bringing arbitration proceedings against States would be well-advised to consider execution options at the outset and draw up a, possibly multi-jurisdictional, enforcement strategy in advance of a final award.

We are ideally placed to advise investors in mapping out multi-jurisdictional strategies to maximise recovery following successful court or arbitration proceedings.

In addition to our International Arbitration practice, we have a market-leading asset recovery team that assists clients in satisfying court judgments or arbitration awards in the UK and globally.

If you would like to discuss investor-state arbitration and/ or asset recovery, please contact one of our specialists below.