The Supreme Court has handed down judgment on 4 March 2026 in Republic of Zimbabwe v. Border Timbers Ltd & Another and Kingdom of Spain v. Infrastructure Services Luxembourg SARL [2026] UKSC 9. Zimbabwe and Spain’s appeals were heard together and they raised the same issues, relating to the registration of adverse ICSID arbitral awards.
The arbitration arose out of Zimbabwe’s Land Reform Programme under which title to certain properties of the Claimants were acquired by Zimbabwe. The Claimants commenced arbitral proceedings against Zimbabwe pursuant to the Zimbabwe-Switzerland Bilateral Investment Treaty which provided for disputes to be referred to arbitration under the ICSID Convention. On 28 July 2015, the tribunal rendered an award in favour of the Claimants.
In 2021, the Claimants made an ex parte application to the English High Court and obtained an order registering the award. Zimbabwe applied to set aside the order, principally on the ground that it was immune from the jurisdiction of the UK courts under the State Immunity Act 1978 (the “SIA”). The Claimants argued that Zimbabwe did not have immunity under the SIA, relying on the exceptions under sections 2 and/or 9 of the SIA. They submitted that: (i) in relation to section 2(2) of the SIA, Article 54(1) of the ICSID Convention constituted a prior written agreement to submit to the jurisdiction of courts of the United Kingdom; and (ii) the section 9(1) exception in the SIA applied as Zimbabwe had agreed to submit the dispute to arbitration.
At first instance, Dias J declined to set aside the registration order and held that state immunity was not in fact engaged on an application to register an ICSID award, which she held to be a purely administrative act.
Zimbabwe appealed. The Court of Appeal rejected Dias J’s analysis. It also held that Article 54(1) of the ICSID Convention constitutes a prior written agreement by which Contracting States had submitted to the jurisdiction of the courts of other Contracting States (for the purposes of section 2 of the SIA). The Court of Appeal considered it unnecessary to decide whether section 9 of the SIA applied, but indicated that national courts are not bound by the determination of an ICSID tribunal as to its own jurisdiction when determining the existence of an arbitration agreement for section 9.
Permission to appeal to the Supreme Court was granted. Two issues fell to be decided by the Supreme Court.
- Did Zimbabwe waive state immunity and submit to the jurisdiction of the English courts by agreement within the meaning of section 2 of the SIA by becoming signatories to Article 54(1) of the ICSID Convention?
- Did Zimbabwe’s alleged agreement to submit the dispute to arbitration mean that the English Court was bound by the ICSID tribunal’s decision that it had jurisdiction for the purpose of section 9 of the SIA?
The Supreme Court, with Lord Lloyd-Jones and Lady Simler giving judgment, unanimously held that (as to the first issue) Zimbabwe has submitted to the jurisdiction of the English courts under section 2(1) of the SIA by virtue of Article 54(1) of the ICSID Convention. It was held that this involved both a domestic-law and an international-law question. As a matter of domestic law, a waiver of immunity by treaty requires a clear and unequivocal expression of the State’s consent. The Supreme Court emphasised that this does not require explicit words such as ‘waiver’ or ‘submission’ to be used, but that nonetheless “[m]eaning is conveyed not only by the express words used but also by what is necessarily inherent in those words” (at [69]). In formulating that test, the Supreme Court characterised Lord Goff’s widely-cited speech in Pinochet (No. 3) [2000] 1 AC 147 as taking “an unnecessarily narrow view of what may constitute an express waiver of immunity” (at [49] ff). As to the international-law question, the Supreme Court had to decide what the correct interpretation of Article 54(1) of the ICSID Convention was, applying the principles of treaty interpretation under the Vienna Convention on the Law of Treaties 1969.
In the Supreme Court’s judgment, upon becoming party to the ICSID Convention, a Contracting State not only assumes the obligation to recognise and enforce ICSID awards, but also agrees that awards to which it is a party will be recognised and enforced in other ICSID States. The Court held that, “[o]n the face of it, this is inconsistent with the preservation of adjudicative immunity” (at [82]). Article 54 reflects an obligation undertaken on a mutual and reciprocal basis and that “necessarily” entails an “express acceptance by each contracting state” that if an ICSID award is rendered against it, then every other Contracting State must exercise jurisdiction to recognise and enforce that award. The submission to jurisdiction on a reciprocal basis is “deduced” (at [93]) and is “readily apparent” (at [95]) from the ordinary meaning of Article 54’s express words. No implication of terms into the ICSID Convention was therefore required.
The Supreme Court found support for its conclusion in the context and purpose of the ICSID Convention. As regards context, it was observed that Article 54 is part of a self-contained regime intended to result in binding and enforceable awards which a domestic court may not re-examine. As regards object and purpose, the Court held that it was sufficient that a major (but not necessarily the entire) purpose of the ICSID Convention would be defeated if a waiver of immunity was otherwise not found. The primary purpose of the ICSID Convention was to protect private investments against sovereign risk, and this purpose would be defeated if adjudicative immunity was preserved.
Given its finding, the Court held that it was unnecessary to determine the second issue on section 9 of the SIA. However, the Court of Appeal’s order remitting Zimbabwe’s set-aside application back to the Commercial Court for directions as its non-immunity defences still stands.
The impact of the judgment will no doubt be felt strongly across the investment treaty arbitration world. The decision aligns the UK’s position with that of other major jurisdictions, including Australia, New Zealand, France, Malaysia and the USA, the courts of which have held that Article 54(1) does constitute a waiver of adjudicative immunity (albeit through different reasoning based on their respective domestic law frameworks of state immunity). The effect of this decision also reflects the English courts’ broader, pro-arbitration policy of preserving the finality of arbitral awards and ensuring that matters relating to the enforcement of awards are dealt with swiftly and speedily.
It remains to be seen how the position under Article III of the New York Convention (which is in materially similar terms) might be affected; the English courts have held that a ratification of Article III in itself does not amount to a waiver of state immunity.
Gresham Legal acted for Zimbabwe, instructing Salim Moollan KC (Brick Court Chambers), Benedict Tompkins (Essex Court Chambers) and Tom Foxton (One Essex Court), with Quinn Smith (GST LLP), also advising.
Philip Beswick (Partner), Christopher Walke (Senior Associate) and John (Ching Jack) Choi (Associate), Gresham Legal