Lettres De Cachet (Fr. cacher, to hide), a kind of warrant formerly in use in France. They were so called in distinction from the lettres patentes, or open letters, which were warrants issued in the name of the king, sealed with his great seal of state, and registered by parliament. The lettres de cachet were closed with the king's petty seal, and were used for ordering persons to quit Paris or France, or to be arrested and imprisoned. They were issued upon the royal authority alone, and not in pursuance of the judgment of a court. Numbers of them were sometimes prepared with a blank for the name of the person, and furnished to the lieutenant general of police at Paris for use in emergencies, and occasionally also to court favorites, who used them as instruments of personal revenge. Abuses of this kind were very frequent during the reign of Louis XV. The punishments directed by these warrants continued during the king's pleasure, and often for long periods. They were abolished by the constituent assembly early in the revolution of 1789.
See Cachet, Lettres De.