International arbitration — the scope of supervisory jurisdiction & anti-suit injunctions following Star Hydro

A recent Court of Appeal decision in Star Hydro Power Ltd (Star Hydro) v National Transmission and Despatch Company Ltd (NTDCL) [2025] EWCA Civ928 considered the limits of foreign court intervention into London-seated arbitration and the availability of anti-suit injunctions to protect English arbitral proceedings and awards. 

At a time when cross-border litigation tactics are becoming increasingly aggressive, enforcement battles are growing more complex and permission has been granted for the Supreme Court to hear an appeal on the matter later in the year, the case and its implications are essential reading for any business involved in international arbitration.

Here, experienced commercial litigator Matthew Moy considers the Court of Appeal’s decision and how the Supreme Court is likely to decide the appeal before giving his five key takeaways for parties with agreements that provide for London-seated arbitration.

What happened in Star Hydro?

Star Hydro and NTDCL (both incorporated in Pakistan) entered into a Power Purchase Agreement (PPA) in which Star Hydro agreed to construct, operate and maintain a hydroelectric plant in Pakistan for 30 years. NTDCL agreed to purchase electricity from Star Hydro during this period, though a dispute emerged over the applicable tariff for the electricity.

The dispute was referred to arbitration pursuant to the PPA which included a London-seat of arbitration (the seat determines the national law that will apply). The sole arbitrator issued an award in Star Hydro’s favour which awarded damages for the purchase of electricity on the higher contractual tariff in the PPA and not on the lower tariff set by the Pakistani regulator.

Before Star Hydro could enforce the award, NTDCL launched proceedings in the Lahore High Court in Pakistan, seeking (i) partial recognition and enforcement of certain paragraphs of the award and (ii) declarations that the remainder of the award — including the payment orders — weren’t enforceable.

NTDCL’s arguments included that the award wasn’t enforceable under Article V of the New York Convention (NYC). The NYC provides that contracting states must recognise arbitral awards as binding and enforce them. However, Article V provides limited grounds on which recognition and enforcement may be refused. 

In response, Star Hydro sought an anti-suit injunction in the English High Court as it considered NTDCL was seeking to challenge the award. This is a court order that restrains a party from starting or continuing legal proceedings in another jurisdiction. The High Court refused to grant the injunction as it considered that the Lahore proceedings were permitted under the NYC and didn’t undermine the award.   

The Court of Appeal unanimously overturned the decision of the High Court and held that while the proceedings in Lahore were framed as a being brought under Article V, they were in fact a “full-throated” attack on the award and therefore fell within the exclusive supervisory jurisdiction of the English courts. An injunction was granted that restrained NTDCL from continuing the Lahore proceedings. 

Court of Appeal: three key findings

1. The court of the seat of an arbitration has exclusive supervisory jurisdiction

While the English court doesn’t have power over foreign courts it does have exclusive jurisdiction over challenges to London-seated awards and is entitled to consider whether proceedings in foreign jurisdictions breach the arbitration agreement. If the seat is London, any challenge to the award must be brought in England and Wales. 

2. Article V of the NYC is intended as a shield, not a sword

It can be used to resist the recognition and enforcement of arbitral awards at the enforcement stage, though it can’t be used to pre-emptively challenge the validity or effect of an arbitral award. This would undermine the finality of awards and the role of the supervisory court as the seat of arbitration. 

3. Anti‑suit injunctions are powerful and remain available

Where foreign proceedings seek to undermine the arbitration agreement or London’s supervisory role, the English courts will intervene to restrain them. Attempts to frame foreign proceedings as recognition and enforcement actions under the NYC will be scrutinised for their true substance and effect.

Ongoing relevance of the Star Hydro decision

The decision has been appealed to the Supreme Court 

The appeal will be heard later in the year. The Supreme Court’s website confirms that the issue to be considered is as follows: “Can the English courts grant an injunction to restrain proceedings brought under the New York Convention in a foreign court that ostensibly seek partial recognition and enforcement of a London-seated arbitral award?”

Since this issue goes to the very heart of global enforcement strategies and comity boundaries, the Supreme Court’s decision will be closely watched. It’s anticipated that the Supreme Court will affirm the Court of Appeal and endorse anti-suit relief to restrain foreign proceedings that seek to attack a London-seated award. 

Parties are increasingly using pre‑emptive foreign proceedings

Cross border disputes increasingly involve parties racing to their home courts to secure a tactical advantage and frustrate enforcement. This is especially the case in regulated sectors or where large state‑owned (or quasi‑state‑owned entities) are involved. Star Hydro confirms that English courts will intervene early to protect against this. 

London’s position as a leading arbitration seat is reinforced 

The Arbitration Act 2025 has already modernised key aspects of the UK’s arbitration framework. Star Hydro further strengthens London’s reputation as a seat with robust judicial protection for arbitral integrity.  Parties choosing London now know that the English courts will defend their arbitration agreement 

Five key takeaways for London-seated arbitration

1. Your choice of seat really matters

It should be stated clearly and will confirm the court that has authority to supervise the award. You should also consider (i) including that the English courts have exclusive supervisory jurisdiction and (ii) adding a no pre-emptive enforcement undertaking. These additions may help to deter satellite litigation in other foreign jurisdictions. 

2. Article V is defensive only

It can’t be weaponised to launch pre-emptive litigation simply to try and derail the enforcement of an award. The English courts will look at the substance and not the form. If an action framed as a challenge to recognition and enforcement under Article V is in fact an attack on the arbitration award or attempt to relitigate issues, the English court will intervene. 

3. Prepare accordingly following an award 

If you’re successful, monitor foreign proceedings so that you can act quickly and seek an anti-suit injunction to stop attempts to relitigate issues outside of England. If you’re unsuccessful and have genuine grounds to challenge, do it in England and within the stipulated deadlines — don’t launch pre-emptive Article V actions in foreign courts as this will invite an anti-suit injunction. 

4. Anti‑suit injunctions are powerful 

The English courts are willing to restrain foreign proceedings that seek to relitigate issues that fall within their exclusive supervisory role. They’re a very robust tool to protect London‑seated arbitration from foreign proceedings. The message from the English courts is clear — if you arbitrate in England, we’ll protect you. 

5. Further clarification is expected

Watch this space — the Supreme Court will be hearing the appeal in the Star Hydro case later in the year. While it’s expected that the Supreme Court will affirm the decision of the Court of Appeal, there’s likely to be some clarification and refinement of the circumstances in which anti-suit injunctions are appropriate and should be ordered by the English courts. 

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If you’re looking for advice on any form of alternative dispute resolution, talk to our commercial litigators today by calling 0333 004 4488, emailing hello@brabners.com or completing our contact form.