Although not always an advocate of violent measures, as deputy to the National Convention with The Mountain, Merlin de Douai voted for the execution of King Louis XVI, and then, as a member of the council of legislation, he presented to the Convention the "Law of Suspects" (17 September 1793), permitting the detention of suspects, (a document backed by Georges Couthon and Maximilien Robespierre). He exercised missions in his native region, and accused General Charles François Dumouriez of having betrayed the country during the Campaign of the Low Countries (after the battle of Neerwinden).