In politics he belonged to the constitutional party. The king created him a marquis. Chasseloup's later years were employed chiefly in putting in order his manuscripts, a task which he had to abandon owing to the failure of his sight. His only published work was ' (Paris, 1801, republished Milan, 1805 and 1811, under the title '). The most important of his papers are in manuscript in the Depot of Fortifications, Paris. As an engineer Chasseloup was an adherent, though of advanced views, of the old bastioned system perfected by Vauban. He followed in many respects the engineer H.J.B. de Bousmard, whose "Essai General de Fortification" was published in 1797 and who fell, as a Prussian officer, in the defence of Danzig in 1807 against Chasseloup's own attack. His front as applied to Alessandria, contains many elaborations of the bastion trace, with, in particular, masked flanks in the "tenaille", which served as extra flanks of the bastions. The bastion itself was carefully and minutely retrenched. The ordinary "ravelin" he replaced by a heavy casemated "" after the example of Montalembert, and, like Bousmard's, his own ravelin was a large and powerful work pushed out beyond the "glacis". His wife, the daughter of François Fresneau de La Gataudière, brought him the Château de la Gataudière, at Marennes, Charente-Maritime; his youngest son, Prosper de Chasseloup-Laubat, was Minister of the Navy under Napoleon III.