UK Supreme Court rules against Royal Embassy of Saudi Arabia clarifying state immunity in claims brought by embassy workers

The Supreme Court delivered its judgment in Royal Embassy of Saudi Arabia (Cultural Bureau) v Costantine [2025] UKSC 9 clarifying whether a State is immune from claims brought by embassy workers employed in an administrative role.

Mrs Costantine worked at Saudi Arabia’s Cultural Bureau in London from 2010 to 2018, initially as a post room clerk and later as secretary to the Head of Cultural Affairs. She brought a claim to the Employment Tribunal alleging discrimination and harassment based on her Christian Catholic faith. Saudi Arabia argued that state immunity barred her claim.

Background

Ms Costantine’s roles were purely administrative — she did not access or analyse confidential information, attend meetings, or make decisions involving sensitive matters. After a brief return to the post room, her employment ended.

In 2018, she brought claims for religious discrimination and harassment under the Equality Act 2010. The Embassy claimed state immunity, but the Employment Tribunal and Employment Appeal Tribunal rejected this, finding her role was not an exercise of sovereign authority. The Embassy appealed to the Court of Appeal but failed to attend the hearing after losing legal representation due to not paying their lawyers. The appeal was dismissed, and Saudi Arabia took the case to the Supreme Court, where it was heard in November 2024.

Supreme Court Judgement

1. Duty to consider application of state immunity

The Supreme Court agreed with Saudi Arabia that the Court of Appeal should have considered state immunity under section 1(2) of the State Immunity Act 1978, even though Saudi Arabia failed to attend the hearing. However, the Supreme Court dismissed the appeal, finding that even if the Court of Appeal had addressed the immunity issue, it would have ruled against Saudi Arabia.

Lord Lloyd-Jones, delivering the judgment with unanimous support from the other judges, upheld the Employment Tribunal’s decision that state immunity did not apply to Mrs Costantine’s role, as the law had been correctly applied to the facts of her employment.

• Whether the correct test for state immunity applied

The Supreme Court has confirmed that administrative and technical workers, like Ms Costantine, are covered by the principles established in the 2017 case of Benkharbouche. In that case, the Court ruled that giving foreign states immunity for employment claims, regardless of the nature of the employee’s work, went beyond what international law requires and violated human rights laws. This led to a change in the law in 2023 to correct the issue.

In this case, the Court ruled that state immunity only applies if the employment itself or the treatment of the employee is closely tied to sovereign activities, like national security or governmental decisions. Since there was no evidence that Ms Costantine’s dismissal was connected to sovereign matters, the Court rejected Saudi Arabia’s immunity claim. This decision confirms that administrative staff can bring claims against foreign states when their work is not directly linked to sovereign authority.

Commentary

The Supreme Court’s decision reinforces the nuanced application of state immunity in employment-related cases. While the principle of state immunity is essential for maintaining diplomatic relations and respecting the sovereignty of foreign states, this case highlights the limits of its application when it comes to administrative and technical staff performing non-sovereign functions. The judgment reaffirms that state immunity does not extend to purely administrative roles that are unconnected to sovereign activities.

The case also underscores the importance of procedural diligence. Although Saudi Arabia did not attend the Court of Appeal hearing, the Supreme Court acknowledged that the immunity argument should have been considered.

The ruling sends a strong signal that employees working for foreign states in administrative capacities have the right to pursue claims for discrimination and harassment, ensuring they are not left without recourse due to the blanket application of state immunity.

Unanswered questions

While the judgment is a positive step in limiting the overreach of state immunity in employment matters, it leaves some critical questions unresolved:

Defining the Boundaries of Sovereign Authority: The Court’s emphasis on whether an employee’s work is closely tied to sovereign activities remains open to interpretation. Future cases may grapple with where exactly the line is drawn, particularly in more complex roles that straddle administrative and policy-based functions.

Inconsistent Application Across Jurisdictions: Although the UK courts have now provided clarity, it remains to be seen how consistently these principles will be applied in other jurisdictions. Different interpretations of sovereign immunity by foreign courts could lead to a lack of uniformity in protecting employees working for diplomatic missions.

Potential Diplomatic Ramifications:Although the decision safeguards the rights of employees, it may raise concerns among foreign states about the erosion of sovereign immunity, potentially complicating diplomatic relations and creating reluctance to employ local staff under comparable conditions.

Conclusion

This case serves as a critical reminder that while state immunity remains a cornerstone of international law, it is not an absolute shield, especially where the rights of individuals are concerned. The decision provides welcome clarity and assurance for employees in similar roles, ensuring that their rights are protected even when working for foreign states.