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Abstract - consulation on AI

Immunity from suit for foreign heads of state: the limited reach of the "commercial activity" exclusion

Posted on 16 October 2023

As part of the long-running "tuna bonds" proceedings, The Republic of Mozambique v Credit Suisse International & Ors [2023] EWHC 2215 (Comm), the English High Court has concluded that, as a current Head of State, the President of Mozambique, Filipe Jacinto Nyusi, is immune from its jurisdiction under the State Immunity Act 1978. The judgment of Mr Justice Knowles considers previously discussed but unanswered questions around the extent of the "commercial activity" exception to the immunity of heads of state and sovereigns, and confirms that it will only operate in respect of commercial activities in the UK.

The background facts

The case concerns claims brought by Mozambique against a number of defendants, including Credit Suisse (against which it has subsequently settled all claims) and Privinvest Shipbuilding SAL (Holding). Mozambique alleges that it was the victim of a $2 billion conspiracy relating to alleged transactions in which it granted sovereign guarantees to secure loans (funded in part by Credit Suisse) entered into by three special purpose vehicles to finance contracts (including a state tuna fishery) for the development of an Exclusive Economic Zone. Mozambique is attempting to revoke its Sovereign guarantees on the loans on the basis that they were procured through alleged corrupt means. A twelve-week trial is currently underway in the English High Court.

Several of the defendants sought to join President Nyusi to the proceedings as a joint tortfeasor or party to the alleged conspiracy, arguing that he should contribute to damages if Mozambique ultimately won the case. The defendants first purported to serve President Nyusi in 2021, but he denied said service was effective. The defendants successfully served President Nyusi in 2023 through the Mozambique Court, relying on alleged activities outside the UK which were said to have occurred primarily before Nyusi became President and which were therefore not within his public capacity or official functions. In response to the 2023 service, President Nyusi argued that he could not be joined as a party to the English proceedings on the basis that he was a serving head of state and therefore enjoyed immunity under international and domestic law. 

The law

Under Article 31(1)(c) of the Vienna Convention on Diplomatic Relations, implemented in the UK by the Diplomatic Privileges Act 1964, a diplomatic agent enjoys immunity from the civil and administrative jurisdiction of the receiving State (in this case, the UK), except in the case of "an action relating to any professional or commercial activity exercised by the diplomatic agent in the receiving State outside his official functions". Section 20(1)(a) of the State Immunity Act 1978 extends this immunity to sovereigns and heads of state, subject to "any necessary modifications".

The key question in this case was therefore whether, when extended to heads of state, the "commercial activity" exception in Article 31(1)(c) only applied to commercial activities undertaken in the UK, or whether a "necessary modification" was warranted so that the exception also covered commercial activities undertaken elsewhere in the world.

The decision

The possibility of modifying Article 31(1)(c) was previously considered by both the High Court and Court of Appeal in Apex Global Management Ltd v Fi Call Ltd ([2013] EWHC 587, [2013] EWCA Civ 642), albeit in circumstances where the issue did not require resolution. At first instance, Mr Justice Vos (the current Master of the Rolls) thought a "necessary modification" might need to be made to Article 31(1)(c) such that the restrictive territorial words "in the receiving State" were excluded. However, Lord Justice Briggs (now Lord Briggs, Supreme Court Justice) in the Court of Appeal disagreed, concluding that it was not clear this was what Parliament intended, and therefore the proposed modification failed the necessity test.

In his judgment in the present case, Mr Justice Knowles observed that, in extending immunity pursuant to the 1978 Act to sovereigns and heads of state, the UK gave statutory effect to customary international law under which heads of state enjoy immunity from proceedings in foreign national courts. The immunity plays an important role in international relations, allowing heads of state to carry out their functions freely without involvement in litigation before a foreign court, and ultimately promoting international co-operation.  

While he did not disagree with Mr Justice Vos' suggestion in Apex that, in 1978, there "was a respectable argument just before the enactment of the [State Immunity Act in 1978] that customary international law had changed by that time so as to prevent sovereign States and their emanations claiming immunity for their commercial activities", Mr Justice Knowles noted that a full exercise had not been undertaken to determine whether the argument was right. He observed that the initial version of section 20(1)(a) of the State Immunity Act had been amended to ensure that heads of state were treated like heads of diplomatic missions "irrespective of presence in the UK". However, as Lord Justice Briggs stated in Apex, extending the "commercial activity" exception in relation to heads of state to activity anywhere in the world would leave a head of state with less immunity when visiting the UK than their ambassador. Mr Justice Knowles also noted that the immunity conferred by section 20(1)(a) only lasts while the head of state is in office, and does not result in immunity from a head of state's own jurisdiction or indeed another state where the alleged commercial activity was undertaken.

Construing section 20(1)(a) of the 1978 Act and Article 31 of the Vienna Convention, so far as possible in a manner according with public international law, Mr Justice Knowles therefore did not consider that modifying the territorial extent of the "commercial activity" exception was "necessary", which is the standard required by the statute. Accordingly, he held that whilst President Nyusi had been validly served in April 2023, he was immune from the English court's jurisdiction in relation to the claims alleged against him in these proceedings, whilst he remains President of Mozambique.


Mr Justice Knowles' decision brings welcome clarity to the remit of personal immunity for commercial activity by current heads of state and sovereigns. As Lord Justice Briggs noted in Apex, this was an important question, previously unresolved in the authorities. 

However, Mr Justice Knowles' reference to the first instance suggestion in Apex that customary international law in 1978 had developed to the point that there was a worldwide exception to a head of state's immunity in relation to commercial activity does raise potential for future arguments in a case where there are sufficient resources and incentive to investigate the position fully, and determine whether that argument is correct.

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