Dr Thomas Lehmann is a Research Fellow in International Arbitration at the National University of Singapore.
A French scholar and Avocat, he specialises in public international law and arbitration, with a focus on energy disputes. He is an alumnus of the Humboldt University of Berlin (Bachelor), Paris-1 Sorbonne University (Bachelor and LL.M.), City University of Hong Kong (LL.M.) and Queen Mary University of London (PhD, 2024).
Thomas’s scholarship spans international investment and commercial arbitration, EU law, energy and climate change law. He is the author of Investment Arbitration and International Climate Change Law: Revaluing Legitimate Expectations (Kluwer) and has authored and co-authored numerous articles and book chapters in leading journals.
Thomas is currently Assistant Editor of the Journal of International Arbitration. He has been a visiting lecturer at University of Ottawa and Queen Mary University, and presented his research internationally, including at Durham University, Paris-1 Sorbonne, and Humboldt University.
Before joining NUS, Thomas conducted the 2025 Queen Mary University and White & Case International Arbitration Survey: ‘The Path Forward: Realities and Opportunities in Arbitration’. Thomas served for four years as Assistant Director of the Executive Course on International Investment Law and Arbitration at QMUL. In 2024-25, he taught tutorials for the commercial arbitration LL.M.
As a practitioner, Thomas was involved in more than 25 high-stakes arbitration cases under ICC, ICSID, LCIA, and UNCITRAL rules. He acted as a lawyer for Gaillard Banifatemi Shelbaya Disputes and trained with the leading international law firms Cleary Gottlieb Steen & Hamilton and Clyde & Co. He also worked at Castineira Law, where he acted as arbitral assistant in ICC proceedings.
He was called to the Paris Bar in 2025 and is fluent in English, French, and German.
RECENT PUBLICATIONS
Books
Investment Arbitration and International Climate Change Law: Revaluing Legitimate Expectations (2025) Kluwer Arbitration Library.
Journal Articles, Book Chapters
‘The Worst Form of Investment Dispute Resolution, Except for All the Others: Defending ISDS in the Net-Zero Transition’ (forthcoming 2025) Les Cahiers de l’Arbitrage / The Paris Journal of International Arbitration.
‘L’arbitrage à l’intersection de la nouvelle économie spatiale et du droit de l’Union européenne’ in Pierre-Jean Thil, Le droit spatial saisi par le droit de l’Union Européenne (forthcoming 2025) Colloques de Droit de l’Union Européenne Bruylant.
‘Book Review: Hong Kong as an Actor in International Economic Law by Professor Julien Chaisse (Hart Publishing)’ (forthcoming 2025) 43 Chinese (Taiwan) Yearbook of International Law and Affairs.
Co-authored with Eliseo Castineira, ‘After Vattenfall, A Science-Based Proposal to Account for Climate Change and Biodiversity in Energy Arbitrations’ (2021) 39 ASA Bulletin 2 286.
‘Police Powers Doctrine: a reliable State Defense in times of Covid-19?’ (2021) 18 Brazilian Journal of International Law 2 73.
