William De Catelle joined White & Case in 2019 and is a senior associate in the EU law practice.

He advises public and private clients on complex issues of EU law, policy and litigation. William has experience across a range of sectors, with a particular focus on the energy sector. He is one of the Firm's specialized attorneys advising on the EU law aspects of the energy transition and is a recognized key lawyer in The Legal 500 for Belgium (2026).

William advises on all aspects of competition law including on State aid, foreign subsidies (FSR), horizontal and vertical agreements, abuse of dominance and merger control, and has led high-stakes negotiations with the European Commission. His practice is also focused on EU trade, digital economy and other regulatory issues, including environmental and climate change law. He co-leads the Firm's global Sustainability & Responsible Business Associate Working Group. William serves as one of two Pro Bono Champions for the Firm's Brussels office, and has acted pro bono on UNEP's Environmental Rule of Law Report and completed a secondment with European Lawyers in Lesvos.

William assists clients in proceedings before the Court of Justice of the European Union and in international arbitration. His experience includes representing energy companies of an EU Member State before the Court of Justice and General Court in an abuse of dominance case, as well as litigating EU law and State aid issues arising in arbitration proceedings.

Prior to joining White & Case, William was a Blue Book Trainee at the European Commission, where he worked in merger control and assisted in the review of some of the largest transactions of 2019. In 2018, he was U.K. National Champion of the Philip C. Jessup International Law Moot Court Competition with the King's College London team. William completed Yale's Financing and Deploying Clean Energy (FDCE) Certificate Program after being awarded a merit-based scholarship.