<P> While serving the government as a silent weapon against political adversaries or controversial writers and as a means of punishing culprits of high birth without the scandal of a lawsuit, the lettres de cachet had many other uses . They were employed by the police in dealing with prostitutes, and on their authority lunatics were shut up in hospitals and sometimes in prisons . </P> <P> They were also often used by heads of families as a means of correction, for example, for protecting the family honour from the disorderly or criminal conduct of sons . The case of the Marquis de Sade (imprisoned 1777--1790 under a lettre de cachet obtained by his wealthy and influential mother - in - law) is a prominent example . Wives, too, took advantage of them to curb the profligacy of husbands and vice versa . </P> <P> In reality, the secretary of state had a delegation, and could issue them at his own discretion, and in most cases the king was unaware of their issue . In the 18th century it is certain that the letters were often issued blank, i.e. without containing the name of the person against whom they were directed; the recipient, or mandatary, filled in the name in order to make the letter effective . </P> <P> Protests against the lettres de cachet were made continually by the parlement of Paris and by the provincial parlements, and also by the Estates - General . In 1648, during the Fronde, the sovereign courts of Paris, by their Arrêt d'Union, procured their momentary suppression in a kind of charter of liberties which they imposed upon the crown, but which was short - lived . </P>

The king is emperor in his own kingdom