Thomas Sebastian

Call: 2012 | 1999 (India) | 2020 (Ireland)

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    BA, LLB (Hons) (NLSIU), BCL (Oxon), MPhil (Oxon)

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    Thomas acts in complex regulatory and commercial disputes. His practice is diverse and spans public international law; commercial dispute resolution; and Chambers’ core practice areas of competition law and EU relations law.

    Recent case highlights include acting for Google in its dispute with Epic Games and acting for the United Kingdom in defending a 2.7 billion euro infraction action brought before the CJEU.

    Thomas has extensive experience in the English courts and before international tribunals. He takes a collaborative approach to his cases and is particularly well-versed in handling disputes which involve economic or regulatory issues.

    • News
    • Public international law, WTO & investment treaties

      Thomas has acted in over 20 treaty cases and has an in-depth understanding of the commercial, regulatory and political factors that give rise to international trade and investment disputes. He has appeared before a wide range of international tribunals including arbitral tribunals established under bilateral investment treaties, WTO panels, the WTO’s Appellate Body and the CJEU. He also has experience of acting in inter-state mediation proceedings.

      Thomas is on the “A Panel” of the UK Attorney General’s list of Public International Law counsel and is ranked in Chambers and Partners and the Legal 500. Earlier in his career, Thomas practiced at the Advisory Centre on WTO Law in Geneva where he represented a wide range of developing countries in inter-state disputes before the WTO.


      Major WTO cases

      • Bahrain — Measures Relating to Trade in Goods and Services, and Trade-Related Aspects of Intellectual Property Rights, DS 527. Acted for Bahrain in its dispute with Qatar regarding sanctions imposed on national security grounds.
      • Australia – Certain Measures Concerning Trademarks, Geographical Indications and Other Plain Packaging Requirements, DS 458. Acted for Cuba in its dispute with Australia regarding plain packaging requirements imposed on tobacco products.
      • South Africa – Anti-Dumping Duties on Frozen Meat of Fowls from Brazil, DS 439. Acted for South Africa in its dispute with Brazil regarding anti-dumping measures imposed on imports of poultry.
      • Thailand – Customs and Fiscal Measures on Cigarettes from the Philippines, DS 371. Acted for Thailand in its defence of fiscal and regulatory measures applied to imported cigarettes.
      • European Communities – Regime for the Importation of Bananas, DS 361. Acted for Colombia in multi-state mediation proceedings regarding the European Union’s import regime for bananas conducted by WTO Director-General Pascal Lamy.
      • United States – Measures Relating to Shrimp from Thailand, DS 343. Acted for Thailand in its challenge to enhanced bonding requirements imposed by the United States on importers of shrimp.
      • Korea – Anti-Dumping Duties on Imports for Certain Paper from Indonesia, DS 312. Acted for Indonesia in its challenge to anti-dumping duties imposed by South Korea on imports of paper.
      • European Communities – The ACP-EC Partnership Agreement, WT/L/ 616, WT/L/625, First and Second Recourse to ad-hoc arbitration pursuant to the Doha Ministerial Decision of 14 November 2001. Acted for Colombia, Costa Rica, Ecuador and Guatemala in their challenges to proposed European Union import tariffs on bananas.
      • European Communities – Export Subsidies on Sugar, DS 283. Acted for Thailand in its challenge to the European Union’s subsidy regime in respect of sugar.
      • European Communities – Conditions for the Granting of Tariff Preferences to Developing Countries, DS 246. Acted for India in its challenge to tariff preferences granted by the European Union to textile products from twelve developing countries.

      Major investment treaty cases

      • UAE investor v European State. Advising a European state in a dispute relating to a real estate investment.
      • French investor v South Asian State, UNCITRAL arbitration, London. Acted for a French investor in a dispute relating to an infrastructure investment.
      • French investor v European State, UNCITRAL arbitration, The Hague. Acted for a European State in a dispute arising from the revocation of marketing authorisations for pharmaceutical products.
      • US investor and Dutch investor v Central Asian State, ICSID arbitration, London. Acted for two energy companies in a dispute relating to the imposition of price controls in the electricity sector on competition law grounds.
      • Millicom v Senegal, ICSID Case No. ARB/08/20, Paris. Acted for a telecom operator in a dispute relating to the revocation of a telecom license.
    • Competition

      Thomas has broad experience across competition and regulatory litigation. He was part of the team defending various airlines in the long-running Air Cargo cartel damages case (work which was recognised with an award for Cartel Defence Litigation of the Year at the Global Competition Review Awards) and is a contributor to the current edition of Competition Litigation: UK Practice and Procedure (2nd Edn, 2019)

      He has a particular interest in conflicts of laws issues as they arise in competition damages claims.


      • Sportradar v Football Data Co and another (CAT). Acted for the Premier League and other UK football leagues in a claim about sports data.
      • FX collective action (CAT). Acted for a defendant bank in the FX collective proceedings.
      • Allianz v Barclays and others (Comm). Acted for a defendant bank in a competition damages claim arising from alleged collusion in the FX market.
      • Trucks competition damages litigation (CAT). Acted for DAF Trucks.
      • Interchange competition damages litigation (SC). Acted for the European Commission as intervener in the Supreme Court.
      • Case C-591/16 Lundbeck v Commission (CJEU). Acted for the United Kingdom as intervener in a case concerning “pay for delay” patent settlements.
      • Arcelik v LG and others (Ch. D) Acted for the claimants in follow-on proceedings concerning the cathode ray tube cartel.
      • GSK and ors v CMA (CAT). Acted for the CMA in various challenges to a decision regarding “pay for delay” settlements of patent litigation.
      • Emerald Supplies Ltd & Ors v British Airways (Ch. D). Acted for Singapore Airlines and various other Part 20 Defendants in the air cargo cartel damages cases.
      • Groupe Eurotunnel SA v Competition Commission and SCOP v Competition Commission (CAT). Acted for the Competition Commission in two judicial reviews of a merger control decision.
    • Commercial

      Thomas acts in commercial disputes both in the English courts and in arbitration and he has a strong understanding of the varying demands of those different fora. He has particular expertise in: (1) disputes governed by Indian law; (2) contractual disputes involving states or state-owned entities; and (3) gas price review arbitrations. Thomas also has experience of acting in arbitration-related applications in the Commercial Court.


      • Naftogaz v Gazprom (SCC Arbitrations). Acted for Gazprom in several complex arbitrations regarding the transit and supply of gas to and through Ukraine. The sums in dispute exceeded USD 100 billion.
      • ICC Arbitration, Singapore. Acted for the Indian party in a private equity dispute regarding exit from a real estate investment. The sums in dispute exceeded USD 100 million.
      • San Leon v Taqa Offshore (Comm). Acted for a UAE defendant in an oil and gas dispute relating to a field in the North Sea.
      • State-owned corporation v UAE investor (Comm). Acted for a state-owned corporation in a s.67 set aside application relating to a concession agreement.
      • European investor v Asian state (Comm). Acted for a foreign investor in a s.67 set aside application relating to an investor-state award.
      • LA Micro v LA Inc and others [2020] EWHC 1405 (Ch D). Acted for a US defendant in a dispute involving the beneficial ownership of shares in a UK computer business.
      • Royal Petrol Trading v Total [2018] EWHC 1272 (Comm). Acted for UAE party in a dispute with Total.
      • LCIA Arbitration, London. Acted for a Mauritius company is a dispute arising out of a renewable energy asset acquisition in India.
      • LCIA Arbitration, London. Acted for a Canadian oil and gas company in a dispute concerning the development of an Indian gas field.
      • ICC Arbitration, London. Acted for a UAE party in a dispute arising out of a cement supply contract.
    • EU, trade & customs

      Thomas is well-placed to advise on the full-spectrum of regulatory, trade and customs-related matters arising from Brexit. He draws on his knowledge of EU law, WTO law, and UK and EU policy processes to design solutions for his clients and frequently acts for UK government departments on complex trade and regulatory matters.

      Thomas also has considerable experience of assisting private respondents in the course of trade remedies and customs investigations and is used to working closely with economic and accounting experts in that context.


      • Case C-213/19 Commission v United Kingdom (CJEU) Acted for the United Kingdom in a multi-billion euro case regarding UK contributions to the EU budget.
      • Advised a Japanese multinational on rules of origin under the EU-Japan Economic Partnership Agreement.
      • Advised a UK law firm on post-Brexit market access to the EU.
      • Advised a stock exchange on GATS and FTA-compatibility of certain policies implemented by a regulator.
      • Advised a UK importer on anti-circumvention rules in connection with an EU anti-dumping measure.
      • Advised a German importer on customs classification issues.
      • Advised a Taiwanese corporation on an Indian anti-dumping investigation.
      • Advised a US corporation on a Chinese anti-dumping investigation.
      • Advised a state-owned corporation on the countervailing duty risks associated with a tax exemption.
      • Advised an investor on the interaction between EU state aid rules and bilateral investment treaty obligations.
    • What the directories say

      Public International Law: “On trade law he’s as good as it gets.” “An outstanding advocate and WTO expert renowned for his trade law knowledge.” “When it comes to WTO law he’s in a league of his own.” – Chambers UK and Chambers Global, 2023

      Competition Law: “A very experienced and assured senior junior, and a very strong drafter.” – Chambers UK and Chambers Global, 2023

      Public International Law: “Tom is an excellent advocate, and has great strategic judgement. This is someone you want in your team for the most complex and challenging international law disputes, particularly if it involves a trade element.”  – Legal 500, 2023

      International Arbitration: Counsel: “Tom has a razor sharp mind and is an excellent advocate – highly recommended.” – Legal 500, 2023

      ‘Insightful and a clear thinker, Tom is user friendly and works well in a team.’ – Legal 500 Asia Pacific 2023 – the English Bar

      Competition: “Tom has a razor sharp mind and is an excellent advocate.” – Legal 500, 2023

      “Stands out as “very experienced in WTO matters”, receiving widespread praise for his top-tier practice.” – International Trade & Commodities, Who’s Who Legal UK Bar 2022

      Recommended in Arbitration, Who’s Who Legal UK Bar 2022

      ‘Insightful and a clear thinker, Tom is user friendly and works well in a team.’ – Legal 500 Asia Pacific 2022 – the English Bar

      Public International Law: “He is user-friendly and approachable. He combines his substantive Indian law experience with his general expertise in international law and arbitration.” – Chambers UK and Chambers Global, 2022

      Competition Law: “He is good at refining the points and getting down to something that is compelling. He is good at drafting and shaping up the arguments.” – Chambers UK and Chambers Global, 2022

      Public International Law: “Tom is absolutely brilliant. He’s the total package – calm, client-friendly, super smart and an excellent advocate.”  – Legal 500, 2022

      International Arbitration: Counsel: “Absolutely brilliant. He’s the total package – calm, client-friendly, super smart and an excellent advocate. He is also without doubt the leading expert at the Bar on WTO and trade law.” Legal 500, 2022

      Competition: “Tom is technically excellent, but his key strength is his approachability. There are no barristers currently working at the Bar in London that offer better client service.” Legal 500, 2022

      Recommended in Trade & Customs, Who’s Who Legal 2021

      Public International Law: “Very clever, thorough and a go-to for WTO matters.”Chambers Global, 2021 – The English Bar – Global-wide

      “He is very responsive, and provides comprehensive advice that takes into account all aspects of the dispute.” – Legal 500 Asia Pacific 2021 – the English Bar

      Competition: “Definitely a future star.” – Chambers UK and Chambers Global, 2021

      Public International Law: “Very clever, thorough and a go-to for WTO matters.” – Chambers UK, 2021

      Public International Law: ‘‘One of the most experienced, if not the most experienced, counsel on trade law issues in the UK, he is also excellent on investment treaty issues.’’Legal 500, 2021

      International Arbitration: Counsel: ‘‘Very responsive and always make himself available to discuss matters and turns work around promptly – his advice is comprehensive and accounts not only for the strict legal merits of the position, but also considers the broader strategic perspective of the case.’’Legal 500, 2021

      Competition: ‘‘Significant expertise in competition disputes and gives high quality advice which is measured and considered; calm and composed and easy to deal with.’’Legal 500, 2021

      “Highlighted by peers as “a leading practitioner in public international law and WTO law”. – Arbitration, Who’s Who Legal UK Bar 2020

      Commercial: “An approachable and hardworking junior of note.” –  Legal 500 Asia Pacific – the English Bar

      Public International Law: “Very well respected in international trade.”Chambers Global, 2020 – The English Bar – Global-wide

      Competition: “Thoughtful and hard-working,” he’s “a calming influence, who works to build a consensus among parties.” “He’s extremely good value for someone of his level of call.” – Chambers UK and Chambers Global, 2020

      Public International Law: “Very well respected in international trade.” – Chambers UK, 2020

      Public International Law: ‘‘Highly rated for state v state disputes.’’Legal 500, 2020

      Receives much applause for his “excellent drafting and industry knowledge” with respondents describing him as “a leading practitioner in public international law and WTO matters” – Arbitration, Who’s Who Legal UK Bar 2019

      Competition: “He is a good team player who is very pleasant to work with.”Chambers UK, 2019

      Public International Law: “Outstanding advocate and WTO expert, renowned for his trade law knowledge.”Chambers UK, 2019

      Public International Law: ‘‘An approachable and hardworking junior.’’Legal 500, 2018

      Public International Law: ‘‘Good at getting to the nub of the situation, and his drafting is concise and elegant.’’Legal 500, 2017

      Public International Law: He combines astute and sound advice with an invaluable “bigger-picture” strategy.’’ Legal 500, 2016

      ”One of the few juniors with a proper understanding of public international law matters.” Leading Junior in Public international Law. Legal 500, 2015

      “A measured and convincing advocate with well-tuned analytical skills.’’  Thomas is ranked as a leading Junior in Public International Law – Legal 500, 2014

    • Additional information

      Thomas was a Rhodes Scholar and studied law at Oxford University as well as the National Law School of India University.

      Prior to transferring to the Bar in 2012, Thomas practiced at the Advisory Centre on WTO Law (an international organisation which represents States in WTO disputes) in Geneva for over seven years. He has also worked within the international arbitration group of a magic circle law firm in London.

      He has strong academic interests and was appointed as a Visiting Professor at the London School of Economics in 2017.


    • Publications

      Thomas’ publications include:

      • Arbitration and the Act of State doctrine [2020] Lloyd’s Maritime and Commercial Law Quarterly 359.
      • Competition Litigation: UK Practice and Procedure, Mark Brealey QC and Kyla George (eds) (Oxford University Press, 2nd Edn, 2019) (contributor).
      • Moral Damages in Investment Arbitration: Punitive Damages in Compensatory Clothing? 29 Arbitration International 45 (2013) (with Stephen Jagusch).
      • The law of permissible WTO retaliation in Bown and Pauwelyn (eds), The Law, Economics and Politics of Trade Retaliation in WTO Dispute Settlement (Cambridge University Press, 2010).
      • World Trade and International Law in Cali (ed), International Law for International Relations (Oxford University Press, 2009).
      • World Trade Organization Remedies and the Assessment of Proportionality: Equivalence and Appropriateness, 48 Harvard International Law Journal 337 (2007).
      • Giving Legal Effect to the Results of WTO Trade Negotiations: An Analysis of the Methods of Changing WTO Law, 9 Journal of International Economic Law 989 (2006) (with Hunter Nottage).

      Shorter pieces can be found at the following links: