He appears in court for major international corporates or financial institutions, practicing principally in banking and finance, corporate and securities litigation, regulatory defence work and white-collar crime. He assists clients in all types of French and cross-border regulatory and criminal investigations. Under Denis’ leadership, his team has developed a significant expertise in internal investigations. He also has substantial experience in product liability litigation, with a strong focus on aviation.

His practice is quintessentially international and he has gained considerable experience dealing with complex cross-border issues, such as conflicts of law and jurisdiction and devising international litigation strategies involving France and other countries. Denis is one of the few practitioners to appear regularly before the courts of French-speaking African countries, where he represents international corporates and financial institutions in commercial and criminal matters.

Denis served in the United Nations Interim Administration Mission in Kosovo in 1999 as a legal advisor to the Head of Mission. He is also the Spokesperson of Droits d'Urgence, a non-governmental organisation providing free legal aid to disadvantaged groups. A former member of the French National Human Rights Commission (by the appointment of the Prime Minister), he teaches international litigation at ESCP Europe, a leading European Business School. He is currently serving as an officer of the Litigation Committee of the International Bar Association. In December 2013, Denis was elected as a member of the Paris Bar Council (Conseil de l'Ordre des Avocats) – the governing body of the Paris Bar. In December 2017, Denis was awarded the Ordre national de la Légion d’honneur, the highest order of merit in France.