This blog has been contributed by Dr Manos Maganaris, Module Convenor for Conflict of laws.
In The Kingdom of Spain v Infrastructure Services Luxembourg S.à.r.l. and another; Republic of Zimbabwe v Border Timbers Ltd and another [2026] UKSC 9, the Supreme Court held that Spain and Zimbabwe could not rely on state immunity to resist the registration in England of the Convention on the Settlement of Investment Disputes between States and Nationals of Other States (ICSID) awards made against them. The decision is important because it treats article 54(1) of the ICSID Convention as a prior written submission to jurisdiction for the purposes of section 2(2) of the State Immunity Act 1978, while preserving immunity from execution under article 55. The judgment is therefore a significant recent authority on the distinction between adjudicative jurisdiction and execution in English conflict of laws
The appeal arose from two separate ICSID arbitrations. In the Spanish proceedings, Infrastructure Services Luxembourg and Energia Termosolar pursued claims arising out of changes to Spain’s renewable energy regime and obtained an award dated 15 June 2018 under which Spain was ordered to pay €112 million, later reduced by €11 million. In the Zimbabwe proceedings, Border Timbers and Hangani Development obtained an award dated 28 July 2015 arising from expropriated land investments, under which Zimbabwe was ordered to pay US$124 million together with interest and further sums in moral damages and costs. In both matters, the successful investors applied to register the awards in England under the Arbitration (International Investment Disputes) Act 1966, and in both matters the respondent states sought to set aside registration on the ground of sovereign immunity under section 1(1) of the State Immunity Act 1978.
The central issue before the Supreme Court was whether article 54(1) of the ICSID Convention constitutes a prior written agreement to submit to jurisdiction within section 2(2) of the 1978 Act. Section 17 makes clear that an “agreement” for this purpose includes an international treaty. The Court therefore had to decide whether accession to the ICSID Convention, and specifically acceptance of article 54(1), necessarily constituted the requisite submission to jurisdiction. The Court answered that question in the affirmative. It held, first, that the domestic test is whether the treaty language contains a clear and unequivocal expression of consent to the exercise of jurisdiction, though explicit words such as “waiver” or “submission” are not required. Secondly, applying orthodox treaty interpretation under articles 31 and 32 of the Vienna Convention on the Law of Treaties 1969, it concluded that article 54(1) necessarily leads to the conclusion that contracting states have consented to recognition and enforcement proceedings in the courts of other contracting states.
The doctrinal force of the judgment lies in its reading of the ICSID Convention as a reciprocal and self-contained regime. Article 54(1) provides that each contracting state shall recognise an award as binding and enforce the pecuniary obligations imposed by it as if it were a final judgment of a court in that state. The Supreme Court treated that language as more than a general undertaking of compliance. In its view, the ordinary meaning of article 54(1) is that each contracting state accepts that an award to which it is a party may be recognised and enforced in the domestic courts of other contracting states. Those mutual and reciprocal obligations were held to be inconsistent with the preservation of adjudicative immunity at the stage of registration. Importantly, the Court stated that this conclusion arose from the express words and structure of the Convention itself and did not depend on implying unstated terms into the treaty.
The most analytically valuable feature of the decision is the distinction it draws between recognition and enforcement, on the one hand, and execution, on the other. The Court stressed that articles 54 and 55 of the ICSID Convention create a deliberate separation between these stages. Article 54 requires recognition and enforcement. Article 55 expressly preserves the domestic law of immunity from execution. That asymmetry was decisive. If immunity from execution is expressly preserved, while no equivalent preservation appears in relation to recognition and enforcement, the implication is that adjudicative immunity is not retained at the earlier stage. In other words, a state may be compelled to face registration proceedings in England even though its assets may still be protected against later coercive measures. This is a powerful clarification of a point that is often obscured in practice by the loose and undifferentiated use of the language of “enforcement”.
That distinction is more than semantic. One of the recurring difficulties in transnational litigation is the tendency to use the language of “enforcement” as though it covers all stages of the post-award process indistinguishably. The Supreme Court resisted that tendency. Recognition is the judicial act by which the award is given domestic legal effect. Execution is the separate coercive process by which assets are attached or seized. The Court’s reasoning reaffirms that private international law depends upon maintaining these distinctions with care. In practical terms, the decision removes one threshold obstacle for successful award creditors, but it does not guarantee recovery. The most contentious disputes may simply move to the execution stage, where the protection afforded to state assets remains substantial.
The judgment is also notable for its method. The Court adopted an orthodox approach to treaty interpretation, relying on text, context, object and purpose, and it treated the ICSID Convention as a self-contained and reciprocal regime designed to ensure that awards are recognised without merits review in domestic courts. It emphasised that one of the Convention’s central purposes is to reduce sovereign risk and facilitate international investment. On that footing, a reading of article 54(1) that left adjudicative immunity intact would have deprived the provision of much of its practical value. The Court further rejected the contention that treaty language can displace immunity only where immunity would otherwise defeat the treaty completely. It was enough that preserving immunity here would substantially hollow out the protection article 54 was intended to provide. That is a strong statement of functional treaty interpretation in an area where domestic immunity law and international dispute settlement intersect.
The judgment is equally careful in its treatment of the travaux préparatoires and comparative authority. The preparatory materials were read as confirming the deliberate preservation of immunity from execution, which explains article 55, but not as supporting any wider retention of immunity from recognition proceedings. The Court also noted a substantial consensus across other jurisdictions, including Australia, New Zealand, Malaysia and the United States, in favour of treating article 54(1) as sufficient to displace adjudicative immunity at the registration stage. In a convention system whose credibility depends in part on consistent interpretation across contracting states, interpretive coherence is itself a substantive value. English law is now firmly aligned with that dominant transnational reading.
One point was left unresolved. The Supreme Court held that it was unnecessary to decide whether section 9 of the State Immunity Act 1978, the arbitration exception, independently removed immunity in these cases, because section 2(2) was sufficient to dispose of the appeals. That restraint was understandable, but it means that section 9 may still require close analysis in future cases where the existence, scope or validity of the underlying arbitration agreement is itself disputed. Even so, the core holding is now clear. Under English law, a contracting state cannot accede to the ICSID Convention and then invoke adjudicative immunity to block the registration of an ICSID award in England. It may still resist execution. It may not resist recognition. For conflict of laws, that is the enduring significance of Spain v Infrastructure Services; Zimbabwe v Border Timbers.