A lettre de cachet was a letter issued by the king of France during the 1700s. The letters were like a ticket that gave the king the power to imprison people or even to exile them from the country if they did something the king did not like. The letters did not need to follow the normal rules of the court because the king could decide what the punishment should be for whatever he wanted. The king usually used these letters to put his enemies in jail or to exile them from the country. People were not allowed to challenge the king's decision and had no rights to appeal or to see justice if they were sent away.