Guillaume de Rancourt’s practice focuses on domestic and international litigation and arbitration.

He also has extensive experience in global investigations and compliance issues, with a particular emphasis on anti-money laundering, anti-terror financing, and anti-corruption matters.

Guillaume’s enforcement work focuses on white-collar defense, including allegations of corporate bribery, criminal and civil fraud, money laundering, and violations of economic sanctions. His practice also includes assisting clients in developing compliance and governance frameworks that respond to the requirements of multiple jurisdictions, including advice on preventative measures, crisis management, and wider strategic issues, focusing in particular on multinational corporations.

Guillaume joined the firm’s Paris office in 2005. From 2008 to 2009 and from 2011 to 2012, he was resident in the New York office.

Notable Experiences

  • NatWest and Crédit Lyonnais in successfully bringing to an end 17 years of hard-fought, billion-dollar litigation under the U.S. Anti-Terrorism Act and Justice Against Sponsors of Terrorism Act when the U.S. Supreme Court denied petitions for certiorari from U.S. Court of Appeals for the Second Circuit decisions affirming the district court’s grant of summary judgment in favor of NatWest and Crédit Lyonnais.

  • A telecom company in annulment proceedings against an ICC award entirely defeating a $15 billion claim brought against our client.

  • A French Bank in an ICC arbitration seated in Paris and governed by French law against its former JV partner in connection with share transfer prices.

  • A global smart card company in an investigation by the World Bank’s Integrity Vice-Presidency into allegations of corruption in relation to a Bangladeshi contract, together with related internal investigations.

  • A pharmaceutical company in ad hoc arbitration proceedings, governed by French law, concerning a claim brought by a chemical company, and related annulment proceedings of the award before French courts.

  • The French State in the criminal investigation and civil proceedings for fraud arising out of the Bernard Tapie arbitral award.

  • A French copper and optical fiber products manufacturer in an ICC arbitration brought by a Chilean cable manufacturer, regarding a post-closing purchase price adjustment dispute.

  • A U.S. coal company in designing their anticorruption compliance policies and procedures.

See More

Selected Activities

Member, ICC, Arbitration and Alternative Dispute Resolution Commission

Member, ICC, Corporate Responsibility and Anticorruption Commission

Member, IBA, Anti-Corruption Committee

Member, ICC France Task Force on “Addressing issues of corruption in international arbitration”

Member, High Legal Committee of the Paris Financial Center (HCJP) working group

Teaches a course on international litigation, arbitration and investigations in a joint master’s program between Columbia Law School, Sciences Po, La Sorbonne and City University of Hong Kong (since 2017)

Lecturer at the Paris Bar School in “Practice of International Arbitration,” (2014 – 2016)


Supply Chain Due Diligence Obligations in Germany, France and the EU: An Overview, March 5, 2024 (with Amélie Champsaur, Mirko von Bieberstein, Sebastian Kummler, Camille Kernevés, Andreas Wildner, and Marc Christopher Baldauf)

France Revises Internal Investigation and Corporate Enforcement Guidelines, April 13, 2023 (with Jean-Yves Garaud, Amélie Champsaur, and Delphine Michot) 

The Anti-Bribery and Anti-Corruption Review – Eleventh Edition, “France” chapter, November 8, 2022

The Anti-Bribery and Anti-Corruption Review – Tenth Edition, “France” chapter, December 17, 2021

Ordre public international de contrôle des sentences : le juge de l’annulation face à l’invocation des sanctions économiques onusiennes, européennes et américaines, note sous Paris, June 3, 2020, SOFREGAZ, Revue de l’Arbitrage, No. 4 (October-December) 2020, pp. 1121-1157 (with Jean-Yves Garaud and Camille Martini)

In Annulment Proceedings Over ICC Award, Paris Court Rules on Nature of U.S., EU, and UN Sanctions, July 10, 2020 (with Jean-Yves Garaud, Laurie Achtouk-Spivak, Camille Martini, and Christopher Moore)

Navigating COVID-19: Best Practices for Managing Compliance Risk, March 26, 2020 (with Jennifer Kennedy Park, Lisa Vicens, Amélie Champsaur, and Caroline Hailey) 

Criminal Settlement Procedures in French Law: an Initial Assessment, Echanges Internationaux, February 2020 (with Caroline Hailey)

Helms-Burton Act: Possible Counterattack for European Companies, La Lettre des Juristes d’Affaires, October 14, 2019 (with Aren Goldsmith)

Trading in International Arbitral Awards: Developments in French Case Law Could Have a Chilling Effect, New York Law Journal, July 12, 2019 (with Aren Goldsmith)

End of Suspension of Title III of the Helms-Burton Act, April 19, 2019

Crédit Lyonnais and NatWest Win Summary Judgment in Long-Running Anti-Terrorism Act Litigation, April 5, 2019

French Criminal Court Orders UBS to Pay a Record EUR 4.5 Billion in Tax Fraud Case, February 28, 2019

Société Générale Enters Into First Coordinated Resolution of Foreign Bribery Case by U.S. and French Authorities, June 6, 2018

Pour une simplification du régime de la responsabilité civile de l’arbitre: plaidoyer en faveur de la notion de “faute lourde professionnelle,” Revue de l’Arbitrage, No 3, July-September 2017 (with Jean-Yves Garaud)

France Implements Sweeping Anti-Corruption Reform, March 22, 2017

France Introduces Sweeping Anti-Corruption Reform, April 19, 2016


October 11, 2023
Heard as an expert in the context of a research project funded by the U.K. Economic and Social Research Council and University of Leicester investigating commercial arbitration in Europe

December 15, 2022
Heard as an expert by ICC France task force on European sanctions against Russia

March 16, 2022
Speaker at Harvard Association for Law and Business and HEC Alumni event

April 8, 2020
Taught (remotely) on Hot Topics in International Arbitration at New York University (with Laurie Achtouk-Spivak)

January 9, 2020
Taught a Master Arbitrage et Commerce International (MACI) course at the firm’s Paris office

Spring 2017
Coach for University of Versailles team for Serge Lazareff International arbitration competition (CIAM)

April 15, 2016
Lecture at the EFB, “Arbitrage, droit international des contrats, clauses attributives de juridiction”

April 8, 2016
Harvard Law Arbitration Discussion Series and Career Event, “The Role, Duties and Powers of Arbitrators: Independence, Neutrality & Corruption”, Harvard Law School