Guillaume Croisant

Guillaume is an all-round litigator specialising in international arbitration and cross-border litigation. He also regularly works on criminal and regulatory investigations as well as compliance matters, with a specific focus on corporate sustainability and ESG. Guillaume’s experience spans various sectors and industries, in particular the financial services, construction, (post-)M&A, commercial contracts, restructuring and insolvency, energy and pharmaceutical sectors.

Guillaume has a decade of experience representing clients as counsel in commercial and investment arbitration as well as related state court proceedings. He has also been appointed as an arbitrator and as a tribunal secretary under the ICC, LCIA, CEPANI and NAI rules. He is the co-chair of the Belgian organisation of under 40-year-old arbitration practitioners (CEPANI40), a member of the board of directors and diversity and inclusion steering committee of the Belgian arbitration association (CEPANI), and a member of the ICC Commission on Arbitration and ADR. He undertook a one-year secondment in the international arbitration practice of our London office in 2017-2018.

Guillaume also devotes a substantial part of his practice to corporate sustainability/ESG, and broader compliance matters (including international sanctions and white collar crime). He lectures on ESG at the Université libre de Bruxelles (ULB). He is a member of the ICC Working Group on Business and Human Rights and of the ICC Commission on Corporate Responsibility and Anticorruption. He contributed the section “Business Integrity” to the 2nd edition of the United Nations Global Compact Guide for General Counsel on Corporate Sustainability and he is the co-editor of the first textbook on Belgian law and sustainability.

Guillaume is recognised by clients and peers in the leading legal directories, including Chambers & Partners, Legal500, Lexology Arbitration (former Who is Who Arbitration) and Leaders League, where he is his described by clients as a “brilliant” and “extremely intelligent” lawyer “with excellent strategic insights to bring disputes to the best end” (Chambers & Partners 2025), “a rising star at the bar, who combines technical excellency with pragmatic strategic advice” and whose “service is unbeatable” (Legal500 2023).

Work highlights

Guillaume has worked on a wide range of business-critical disputes. Those that can be disclosed include representing and advising:

• an Asian multinational in a USD 100M post-M&A ICC arbitration 
• a global financial institution in a USD 250M CEPANI arbitration and parallel Belgian court proceedings 
• a global bank, in Belgian and English court proceedings pertaining to the enforcement of an arbitral award against an Asian State and attachments over assets worth US$22bn
• an African State in the Belgian annulment proceedings of a €1bn investment arbitration award
• a global bank before the EU institutions, an LCIA arbitral tribunal, the European Court of Human Rights and local courts in its capacity as creditor for an amount of US$1bn of an Eastern European group benefitting from protectionist measures adopted by its home State
• various multinationals as global ESG counsel, covering the full spectrum of sustainability matters (ESG litigation and greenwashing, supply chain due diligence, sustainability reporting, etc.)
• a Belgian multinational in bribery and money-laundering parallel investigations across five jurisdictions

Guillaume is the co-editor in chief of Belgium’s leading business law journal (Revue de Droit commercial belge / Tijdschrift voor Belgisch Handelsrecht), and he is the author of numerous contributions in treaties and legal journals. He is regularly invited to act as a speaker in academic and industry seminars, and to comment topical subjects relating to his practice in the media.

Guillaume has worked on a number of pro bono and community investment initiatives of the firm, including by delivering trainings on business and human rights in Kenya (with Advocates for International Development), drawing up a European database of asylum law (with the European Council on Refugees and Exiles; finalist of the 2016 European Award for Exemplary Partnership in the Public Interest) and representing aisle seekers before the European Court of Human Rights (Rule 39 Initiative of the Italian Coalition for Civil Liberties and Rights; 2023 PILnet Global Partnership Award).

Guillaume was admitted to the Brussels bar in 2014 (Prix George Boels). 

He holds a Magister Juris from the University of Oxford (Brasenose College), where he studied on the Wiener Anspach Foundation Scholarship for Excellence, and a Bachelier en droit and a Master en droit from the Université libre de Bruxelles, where he graduated top of the year (Prix René Marcq, Prix André Bruyneel, Premier Prix d’Excellence). 

Guillaume also completed the ESG Accelerator Programme of the University of Oxford (Saïd Business School) in 2021.