After the abdication of Napoleon in 1814, Dejean joined the Provisional Government, and performed the difficult task of extraordinary commissioner to Comte d'Artois (the future Charles X). He was also appointed, a Peer of France, Governor of L'Ecole Polytechnique and Chairman of the Committee for the Liquidation of Arrears. But in 1815, having accepted service under Napoleon Bonaparte during the Hundred Days, he was removed from all public offices on return of the Bourbon regime.
