D'Estournelles represented France at The Hague Peace Conference in 1899. He attempted to get acceptance for the principle of compulsory arbitration, but this was not possible. After the conference he strongly promoted the Permanent Court of Arbitration, and he founded the French Groupe de l'Arbitrage in 1903. D'Estournelles advocated Franco-German conciliation and wanted a European federation.
Member of the Commission of the Permanent International Peace Bureau
Full name: Paul Henri Benjamin Balluet, Baron d'Estournelles de Constant de Rébecque.
Morel suggested d'Etournelles de Constant if the prize were to be divided. His primary choice was Bertha von Suttner.