Nigeria Wins $3.38bn Mambilla Arbitration Battle As ICC Rejects Sunrise Claims

Nigeria has won a major international arbitration battle over the long-delayed Mambilla Hydroelectric Power Project, after an International Chamber of Commerce (ICC) tribunal in Paris rejected claims by Sunrise Power and Transmission Company Limited that had put the country’s potential financial exposure at more than $3.38 billion.

The ruling, issued on September 17, 2026, is a significant development for the proposed 1,500MW Mambilla power project in Taraba State, which has been stalled for years by a combination of legal, contractual, financing and implementation challenges.

President Bola Ahmed Tinubu welcomed the decision, describing it as the removal of what he called the biggest legal obstacle to the project’s progress.

The dispute dates back to a 2003 agreement concerning the development of the Mambilla project. Sunrise Power subsequently commenced arbitration proceedings against Nigeria at the ICC in October 2017, initially seeking about $2.35 billion over an alleged breach of contract.

The parties later entered into a settlement agreement in 2020 under which Nigeria was to pay Sunrise $200 million. A subsequent disagreement over the implementation of that agreement led to another arbitration.

In the latest proceedings, Sunrise sought about $680 million, including the settlement sum and interest. A separate claim connected to disputes over the development of the Mambilla project was valued at more than $2.7 billion in compensation and interest.

Together, the related claims created potential exposure of more than $3.38 billion for Nigeria.

The ICC tribunal rejected Sunrise’s claim that Nigeria had breached its obligations under the settlement agreement and its addendum. It also dismissed the company’s request for Nigeria to pay $400 million, comprising the $200 million settlement sum and an additional $200 million claimed as a default payment.

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The tribunal further held that Leno Adesanya, the promoter of Sunrise Power, was bound by the arbitration agreement under the settlement arrangement. It also confirmed its jurisdiction over Nigeria’s counterclaim against Adesanya and his firm.

Rather than ordering Nigeria to pay the amounts sought by Sunrise, the tribunal directed Sunrise and Adesanya to reimburse Nigeria for 75 per cent of its legal fees and expenses incurred in the arbitration.

The legal costs were assessed at approximately $11.82 million. About $2.5 million is expected to be recovered from funds held in escrow by the ICC, while Sunrise and Adesanya are required to pay the remaining $9.32 million, with interest at 10 per cent annually, compounded annually, from notification of the final award until payment.

The tribunal also fixed the arbitration costs at approximately $1.66 million, with Sunrise and Adesanya responsible for 75 per cent and Nigeria responsible for the remaining 25 per cent.

The three-member tribunal was chaired by Melaine van Leeuwen, with Stavros Brekoulakis and Simon Nesbitt serving as co-arbitrators. Nigeria’s external legal team was led by Elizabeth Oger-Gross and Tolu Obamuroh of Paul Hastings LLP.

The outcome ends a major phase of a dispute that has followed the Mambilla power project for nearly a decade in international arbitration and more than two decades from the original project agreement.

The original proposal envisaged a 3,050MW hydroelectric plant in Taraba State under a build-operate-transfer arrangement. The project was subsequently revised as the government sought to reduce its cost and improve its prospects of attracting financing.

In 2021, the Federal Government announced that the planned capacity would be reduced by about half, from 3,050MW to approximately 1,525MW. The scheme was subsequently rescoped to around 1,500MW to make it more financially viable and “bankable” for lenders.

The original project had been associated with an estimated cost of roughly $5 billion to $5.8 billion, while the rescoped project has been put at around $4 billion in previous government discussions.

The prolonged delay has meant that the Mambilla scheme has yet to become an operational source of electricity despite its potential to significantly increase Nigeria’s generation capacity.

President Tinubu, in his reaction to the ICC ruling, commended Attorney-General of the Federation and Minister of Justice, Lateef Fagbemi, officials of the Federal Ministry of Justice and Nigeria’s external legal team for their role in defending the country.

He also acknowledged former President Olusegun Obasanjo and the late former President Muhammadu Buhari, who testified during the arbitration proceedings, as well as former Ministers of Power Babatunde Fashola and Suleiman Adamu and other witnesses and experts.

Tinubu also credited the National Security Adviser and the Economic and Financial Crimes Commission (EFCC) for their roles in the broader matter.

The President said Nigeria remained committed to working with genuine investors and honouring its legal obligations while defending the country against claims it considers detrimental to the national interest.

The original 2003 contract has also been the subject of separate domestic legal proceedings and investigations. Tinubu said the contract was not authorised by the Federal Executive Council (FEC). Those domestic proceedings are distinct from the ICC arbitration, which has now been decided in Nigeria’s favour.

The arbitration victory, however, does not mean that the 1,500MW Mambilla project is immediately ready for construction or electricity generation.

The government still has to address major issues involving project financing, construction, engineering, transmission infrastructure and implementation arrangements. Previous plans have included financing discussions involving the Export-Import Bank of China, while the project’s restructuring was intended to improve its bankability.

With the arbitration dispute now resolved, the focus shifts to securing the funding and completing the arrangements required to move the Mambilla project from a long-delayed proposal to actual construction and, ultimately, electricity generation.

Nigeria Wins $3.38bn Mambilla Arbitration Battle As ICC Rejects Sunrise Claims