A member of La Sapinière, he espoused intransigent integralist views in his various books and his weekly newspaper, Semaine religieuse de Cambrai.

Delassus was one of the main proponents of Judeo-Masonic conspiracy theory and remains an influential author among French far-right circles.

Delassus believed in the existence of a conspiracy between Jews and Freemasons with the goal of destroying European Christendom.

Le temple maçonnique voulant s’élever sur les ruines de l’Église (The Anti-Christian conspiracy.

[1]In his 1913 book La Mission posthume de sainte Jeanne d'Arc et le règne social de Notre-Seigneur Jésus-Christ ("The posthumous mission of Saint Joan of Arc and the Social Kingship of Our Lord Jesus Christ") Delassus defends a providential view of history, considering French national identity as inseparable from Catholicism and monarchism.