Chauveau-Lagarde distinguished himself by his moral courage under the Reign of Terror, where he defended moderate Girondins such as Jacques Pierre Brissot, his fellow countryman from Chartres.

He also defended Louis-Marie-Florent, duc du Châtelet; Jean-Sylvain Bailly; Madame Roland; Geneviève de Brunelle and Charlotte Corday, who had assassinated Marat.

In Corday's case, Chauveau-Lagarde knew that the judgment had been decided in advance, and limited himself to pleading in her defense "the exaltation of political fanaticism" that had placed the knife in her hand.

He took on the 1793 defense of Marie Antoinette so zealously that the Comité de sûreté générale became suspicious; once sentence had been pronounced on the Queen, he was summoned before the committee and accused of having defended her all too well; but he managed to justify his actions.

Other notable cases included defending a group of women accused of having welcomed the invading King of Prussia with sugared almonds.

[citation needed] Following the passage of the Draconian law of 22 prairial an II (10 June 1794), which suppressed the role of lawyers for the defense of those accused before the tribunals, he withdrew to his native city.