International arbitration

Investment treaty arbitration

A&O Shearman is a world leader in investment treaty arbitration, with a proven track record of success for investors and States across more than 100 investor-state disputes. 

International arbitration
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“A&O Shearman is highly regarded for its stellar track record in representing sovereign states and corporates in high-value investment treaty disputes.”

Chambers & Partners UK, 2026

With a multilingual team of over 50 investment treaty specialists spread across 17 countries, we combine global breadth with local strength and industry expertise.

This enables us to provide teams that are custom-tailored to the specific nation, industry, language and legal system of the dispute.  We have some of the leading practitioners in this field, with several partners holding positions in the leading arbitral institutions for investor-state disputes. This includes membership of the ICSID panel of arbitrators, the Permanent Court of Arbitration and the ICC Court of Arbitration.  

Investors and states trust us with their most high-stakes disputes, including numerous repeat instructions.  Our balanced practice enhances our credibility before international tribunals. It also enables us to anticipate opponents’ likely arguments and design strategies to overcome them.   

Key strengths

A global powerhouse

We have handled over 100 investor-state disputes – in 52 countries across Africa, Asia, Europe, the Middle East and the Americas – under the ICSID Convention, the New York Convention and all major arbitral rules including the UNCITRAL Arbitration Rules.  Our sector experience includes multiple investment treaty cases in the fields of renewable energy, oil and gas, mining, infrastructure projects, finance, telecoms, technology, steel production and cement production.  

We are one of the leading firms in the world in terms of the number of investment treaty cases on which we have acted under the ICSID Convention (more than 80) and also in terms of the number of cases under the multilateral Energy Charter Treaty (ECT). 

What sets us apart?

We pride ourselves on delivering bespoke and innovative solutions tailored to our clients’ needs.

Our investment treaty specialists (including several King’s Counsel and Senior Counsel) routinely lead our clients’ advocacy before international tribunals, avoiding the costs of separate counsel teams.  But achieving success in investor-state disputes often calls for more than just advocacy.  It can require deep industry experience, local in-country teams, supervised use of agentic AI, quantum expertise, tax advice, sanctions advice, expertise in sovereign immunity, and the ability to handle related litigation before national courts.

Our team is designed to meet these challenges, wherever and whenever they arise.   For example, we have market-leading practices in every major seat for investor-state arbitration, including England, France, Hong Kong, the Netherlands, Singapore and the United States.  We have advised clients on many of the most cutting-edge issues in those countries, including set-aside applications, enforcement proceedings and anti-suit injunctions.

Our early adoption of AI to drive cost-effective solutions for our clients is reflected in the Financial Times voting us as the world’s most innovative law firm in 2025.    

Unlike boutique arbitration firms, we work closely with our market-leading finance and corporate teams to ensure that our clients achieve successful outcomes: not just successful awards.  This includes advising numerous arbitration clients, private equity firms and third-party funders on corporate solutions such as assignments of awards, asset-tracing exercises, M&A transactions, joint venture agreements and wider corporate settlements.

A track record of success

We have achieved successful outcomes for clients in more than 80% of our investor-state disputes.

In the vast majority of cases for investors, we have achieved favourable awards or have reached a settlement with the state that is to our clients’ advantage. Our team’s successes include obtaining the largest-ever investment treaty award (over USD50 billion in damages, against the Russian Federation) and awards totalling over EUR700 million in ten separate investor claims under the ECT against the Kingdom of Spain.

When representing States, in many cases we have successfully defeated the claims at an early jurisdictional stage and, in other instances, achieved settlement of the dispute on terms favorable to the State. Even where the matter has proceeded to a final hearing, we have either defeated the claim on the merits, or shown the value of claim to be drastically exaggerated, resulting in only a small fraction of the damages sought being awarded. 

Representative matters for investors

  • The majority shareholders in the former Yukos Oil Company, in three UNCITRAL arbitrations under the ECT against the Russian Federation in relation to the expropriation of their investment. The Tribunal ordered the Russian Federation to pay over USD50 billion in damages and to reimburse 75% of our clients’ legal fees and 100% of the arbitration costs.
  • Over 30 international investors in 12 separate claims against the Kingdom of Spain under the  ECT in relation to investments in the renewable energy sector and retrospective changes made by Spain to the regulatory framework. We have achieved significant damages awards for our clients in ten concluded cases, worth a total of more than EUR700 million.  
  • Overseeing the enforcement of multiple ECT awards against Spain globally, including securing recognition and enforcement orders in the Australia, England, Singapore and the United States.  For example, we represent NextEra Energy in the leading decision on enforcement of intra-EU ECT awards under the ICSID Convention in the United States, in defence of Spain’s pending petition for certiorari to the United States Supreme Court, and in the first-ever recognition of an ICSID award in Singapore.  
  • Two oil and gas companies, in their investment treaty claim against a South East Asian State and its state-owned national petroleum company. The very substantial dispute arose from Production Sharing Contracts for the exploration, development and production of oil and gas located offshore. The dispute was settled in return for a USD800m payment to our clients. 

 

  • Nissan, in its investment claim against India under the Economic Partnership Agreement between Japan and India, arising out of unpaid incentives due to Nissan from an Indian state government. After securing an award dismissing India’s jurisdictional objections, the claim was settled, with Nissan receiving payments in the region of USD350m.
  • Vodafone in two high-profile investment treaty claims against India and related proceedings before the Singaporean courts. These culminated in India agreeing to nullify retroactive withholding tax demands of more than USD 5 billion (including interest and penalties) in a complete victory for Vodafone.
  • British Caribbean Bank (BCB) and Dunkeld International Investment Limited, in UNCITRAL investment treaty claims against Belize arising out of the Government’s nationalisation of the main telecommunications provider in Belize, Belize Telemedia. BCB was awarded its full claim, plus interest and costs (USD48m) and Dunkeld awarded USD180m, plus interest and costs.
  • Successfully defending nine applications for annulment of awards under the ICSID Convention, as well as prevailing in rectification proceedings under that Convention.  
  • Beyond these concluded cases, we are also acting for many prominent investors in pending investment treaty claims and contract-based arbitrations at ICSID under the UNCITRAL Rules.  The investors who have entrusted us with these high value disputes include ArcelorMittal, Chevron, Huawei, Korea National Oil Corporation, Rockhopper Italia, Telenor and Vedanta Resources.  

Representative matters for states

  • The Republic of Korea in successfully defending an ICSID claim brought by Feng Zhen Min under the China-South Korea BIT in relation to the alleged expropriation of real estate company and court proceedings that led to his imprisonment on charges of fraud and embezzlement. Claims were dismissed in full, and Korea awarded its costs. We now act for Korea in ICSID annulment proceedings launched by Mr Min.
  • The Kingdom of Cambodia in successfully defending a claim brought at ICSID by two Chinese investors, Qiong Ye and Jianping Yang, in the telecoms sector. The Award denied jurisdiction over Ms Yang’s claim and Mr Ye’s denial of justice and expropriation claims were denied. Cambodia was awarded 80% of its legal and other costs (excluding fees and expenses of the Tribunal and ICSID).
  • The Islamic Republic of Pakistan in successfully defending investment treaty claims of nearly USD 600m brought separately by Mauritian and U.K. investors in an LPG-import terminal and distribution business.  We also defeated challenge proceedings brought by the investors in the English courts.

 

  • The People’s Republic of China (PRC) in ICSID by Hela Schwarz GmbH. The claims were brought under the China-Germany bilateral investment treaty. In 2025, the Tribunal partly upheld the PRC’s jurisdictional objections and dismissed the remainder of Hela Schwarz’s claims on the merits. This is the first investment treaty arbitration that the PRC has won on the merits.
  • The Kingdom of Morocco in defending a claim of USD 2.7 billion brought by Corral Morocco Holdings AB in relation to investments in the privatisation of SAMIR, the owner and operator of Morocco’s only oil refinery. The Tribunal awarded the investor less than 6% of the amount claimed, which was further reduced in rectification proceedings. We also act for Morocco in pending proceedings to partially annul the award.
  • The Republic of Panama in successfully defending investment treaty brought by Omega Engineering LLC and Mr Oscar Rivera. The dispute relates to infrastructure construction projects. The claims were brought under both the U.S.-Panama bilateral investment treaty and trade promotion agreement. Claims were dismissed at the merits stage.
  • Beyond these concluded cases, we are currently representing multiple States in high-stakes pending investment treaty disputes. Our sovereign clients include the Kingdom of Bahrain, the Grand Duchy of Luxembourg, the Kingdom of Morocco, the Swiss Confederation and Ukraine.    

Meet our team

Our lawyers have the skills and experience to handle our clients' most complex challenges. Meet them below. 
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Awards and accolades

Tier One firm

Legal 500 UK, Public International Law 

“A&O Shearman's teams are particularly active in high-profile ECT and BIT cases, showcasing the firm's capacity to coordinate complex investor-state mandates between its offices.” 

Chambers Europe-wide, International Arbitration

“The practice notably stands out for its strong BIT and investment treaty expertise: it is representing Ukraine and its entities in a number of challenging cases linked to Russian sanctions. “  

Legal 500, France, Disputes Resolution: International Arbitration

“A&O Shearman has a strong track record in representing sovereign states and corporates in high-value investment treaty disputes. It has considerable experience carrying out its own advocacy before courts and tribunals.” 

Chambers UK, Public International Law

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