Key takeaway

The UK Supreme Court has now heard the appeal in Star Hydro Power Limited v National Transmission and Despatch Company Limited (UKSC/2025/0150). The two-day hearing took place on 15 and 16 June 2026 before five justices (Lord Sales, Lord Leggatt, Lord Burrows, Lady Rose, and Lord Doherty). What began as a commercial tariff dispute over a hydroelectric plant in Pakistan has grown into proceedings with significant implications for international arbitration. As of the time of writing, the case is listed as awaiting judgment. The UK Supreme Court routinely reserves judgment following a hearing, with decisions typically delivered weeks or months later.

Star Hydro v NTDCL: background to the dispute

The dispute arises from a 30-year Power Purchase Agreement entered into in 2012 between Star Hydro Power Limited (“SHPL”), a special purpose vehicle backed by South Korean investors, and National Transmission and Despatch Company Limited (“NTDCL”), Pakistan's state-owned electricity transmission entity. SHPL agreed to construct and operate a 147 MW hydroelectric power plant, with NTDCL purchasing electricity at a fixed tariff.

When project costs rose, SHPL sought a tariff adjustment. Pakistan’s regulator, the National Electric Power Regulatory Authority (“NEPRA”), instead reduced the project cost and set a lower tariff. SHPL commenced a London-seated LCIA arbitration. On 7 May 2024, the arbitrator issued a final award in SHPL’s favour, fixing the project cost at US$378.3 million, confirming a tariff of 10.3632 PKR/kWh, and ordering NTDCL to pay the financial difference.

Read our earlier article on Star Hydro Power v NTDC and exclusive English jurisdiction over London-seated arbitration awards for analysis of the Court of Appeal decision.

New York Convention proceedings in Pakistan

Rather than challenge the award in the English courts, NTDCL commenced proceedings before the Lahore High Court in August 2024, framed as an application for partial recognition and enforcement under Pakistan's Recognition and Enforcement (Arbitration Agreements and Foreign Arbitral Awards) Act 2011, which implements the New York Convention in Pakistan.

The application was carefully constructed. NTDCL did not seek enforcement of the part of the award requiring payment. Instead, it asked the Pakistani courts to recognise the arbitrator's finding that NEPRA holds exclusive jurisdiction over tariffs, and to declare the award unenforceable on public policy grounds. The Lahore High Court made an interim order suspending SHPL's invoices. SHPL applied to the English Commercial Court for an anti-suit injunction to restrain the Lahore proceedings.

Read our article on challenging arbitration awards and the limits of the New York Convention for related analysis of Convention-based challenges to arbitral awards.

Anti-suit injunctions and London-seated arbitration awards

The High Court refused the injunction, finding that the Lahore proceedings were a legitimate use of the New York Convention and did not amount to a challenge to the award.

The Court of Appeal took the opposite view. In a unanimous decision ([2025] EWCA Civ 928), it granted the injunction, holding that NTDCL's proceedings were in substance a direct attack on the award designed to circumvent the exclusive supervisory jurisdiction of the English courts. The Court confirmed that the English courts hold exclusive supervisory jurisdiction over challenges to London-seated awards and that the New York Convention operates as a shield, not a sword. Article V provides limited grounds to resist enforcement when it is sought; it cannot be used offensively to mount a pre-emptive challenge before any enforcement action has been brought.

What question must the Supreme Court decide?

The Supreme Court must now determine whether the Court of Appeal's analysis is correct. The certified issue 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?

While the Court of Appeal's position has attracted broad support within the London arbitration community, it has not gone unchallenged. NTDCL's Lahore application did not seek to set aside the award, as only the English courts have that power. A declaration by the Lahore High Court would have legal effect only in Pakistan and would not bind the English courts. On the opposing view, the Court of Appeal's decision has been said to overstate the primacy of the seat and imposes on foreign sovereign courts a contested reading of the Convention.

New York Convention Article V: shield or sword?

If the appeal is dismissed, Article V of the New York Convention will be confirmed as a purely defensive tool, unavailable for pre-emptive use by award debtors. This would send a strong signal that the English courts will robustly protect London-seated awards from tactical interference in foreign jurisdictions.

If the appeal is allowed, the Supreme Court will have confirmed that the English courts' supervisory jurisdiction does not extend to restraining genuine recognition or enforcement applications before the courts of other Convention States. While this may be seen as affirming judicial comity, such an outcome could open the door to a wave of pre-emptive parallel proceedings, allowing losing parties to obtain advantageous local rulings before a winning party has had any opportunity to pursue enforcement.

Why does the Star Hydro Supreme Court judgment matter?

Whatever the outcome, this decision will shape the landscape of international arbitration for years to come. For businesses with London arbitration clauses in their international contracts, it will clarify precisely what protection those clauses offer if a counterparty pursues parallel proceedings in its home courts. For practitioners, it will define when English anti-suit relief is available. For courts in other jurisdictions, it will offer authoritative guidance on the relationship between seat-court supervision and Convention-state enforcement, a topic that has generated significant academic debate, including a peer-reviewed commentary published this year in Lloyd's Maritime and Commercial Law Quarterly.

London's standing as one of the world's leading arbitration seats rests in part on the English courts' consistent approach to upholding arbitration agreements. The Supreme Court's judgment in Star Hydro v NTDCL will be an important test of that commitment.

Barnes Law’s Arbitration team advises clients on London-seated arbitration, anti-suit injunctions, recognition and enforcement of arbitral awards, New York Convention issues and cross-border arbitration disputes. For more information, please contact our Arbitration lawyers to discuss how we can support you.

Written by Barnes Law Managing Partner Yulia Barnes.