The real reserved order was an alegal document by which a Spanish monarch ordered to skip the ordinary judicial procedures and act directly on any person, who, in this way, was devoid of any right and in a legal limbo, without being heard, but imprisoned, if not dead, without being judged or even know what was the accusation for which he had been locked up; as such it was one of the most characteristic procedures of the form of government called Absolutism or Despotism and has also been used by dictatorships and some secret services of democratic governments.
In the French absolutist state of the sixteenth to eighteenth centuries the equivalent document was the so-called lettre de cachet. According to the Abbe Augustin Barruel: The only real vice that could be objected to the French government considered in itself and the only one that knew despotism and arbitrariness was the use of the reserved orders of the king (lettres de cachet); certainly illegal orders and that no real law could authorize in a civil government, because by these orders a citizen lost his freedom without being heard, nor judged legally. I do not want to excuse this abuse by saying, which is very true, that the citizen and the plebeian were not exposed to them, that they usually did not fall but on the schemers surrounding the court or on the seditious writers or on the high magistracy in his differences with the ministers, but I will say that the origin and preservation of these reserved orders is not what is commonly believed to be an effect of the despotism of the kings. Their real cause was in the moral character and opinion of the French themselves, [...] whose use they themselves requested. In fact, such was the opinion or way of thinking of families, even of the least distinguished in France, who considered themselves dishonored when they were publicly and legally punished by a son, brother or close relative. From here it originated that, to avoid this legal judgment, the relatives asked the king to send a bad vassal to lock up whose bad behavior fell on the family as it was a dissipater who ruined it, a criminal who infammed it or exposed it to an infamy, exposing himself to be judged and punished publicly by the courts. If there was hope of amendment, the order was correctional and for a limited time; but, if the crime was serious and truly infamous, the offender was condemned to perpetual confinement. It is not to be thought that these orders should be reserved for a simple demand and without any information. For the ordinary after presenting the petition to the king, he referred this to the mayor of the province and he sent a subdelegate to inform the relatives, hear the witnesses and form a verbal process of their depositions. On these reports that were sent to the ministers, the reserved order was granted or denied. Although these reserved orders did not generally include the vulgar, nevertheless, the king did not always refuse to grant them to the lower classes ... Augustin Barruel, Memoirs to serve the history of Jacobinism, t. II, Perpignan: J. Alzire, 1827, pp. 45-46.
A similar use was made in Spain to the reserved order, but it was also used to imprison without trial dissidents or political enemies, or descendants of rebels whose mere existence was dangerous, such as Tupac Amaru, for example, during the reign of Carlos III.
wiki
