Ruyssen was the President of the Association de la paix par le droit, the most important peace organization in France, which is widely known throughout the world through its official organ "La Paix par le Droit," and a member of the International Peace Bureau in Berne.Introduction to Ruyssen's "What is a Nationality?" in International Conciliation no. 109, 1917. Retrieved 11 March 2014.
