The collection comprises a single 18th century manuscript concerning the definitions of "reserved cases," in other words: crimes or sins which would result in excommunication for Catholics. Examples of such cases are homicide, abortion, sacrilege, public blasphemy, certain dealings with the devil, clandestine marriages, falsification of papers, arson, and Spaniards coming to Mexico while leaving their wives in Spain for more than five years.

The manuscript consists of three sections: Privilegios de Indios, which relates special privileges granted in this matter to the Indians; Explicación de los casos reservados sinodales de Mexico, which contains a paragraph on each crime; and Excomuniones Latae reservadas en este Arzo bispado de Mexico, which lists fourteen crimes and discusses the first eleven. The paleography and type of sins discussed, some of which were not reserved later, suggest a mid-18th century date.

An English summary is filed with the manuscript.