- and he goes on to say that the violator of this law should be made a life-long, ignominious wanderer.
Notably, neither this canon nor the law of the Decretum purports to enact for the first time the secrecy of confession. The great fifteenth century English canonist William Lyndwood speaks of two reasons why a priest is bound to keep secret a confession, the first being on account of the sacrament because it is almost (quasi) of the essence of the sacrament to keep secret the confession. (Cf. also Jos. Mascardus, De probationibus, Frankfort, 1703, arg. 378.)
Priests may not reveal what they have learned during confession to anyone, even under the threat of their own death or that of others. For a priest to break confidentiality would lead to a latae sententiae (automatic) excommunication, the lifting of which is reserved to the Holy See—in fact, to the Pope himself (Code of Canon Law, 1388 §1). It is presumed such a breach could be forgiven only with the lifting of the authority of that priest to ever hear confessions again, and a requirement that the priest undertake an extended period of penance, perhaps in a monastery. In the Early Modern period, some casuists (Thomas Sanchez, etc.) justified mental reservation as a form of deception which does not involves outright lying, in specific circumstances such as the seal of the confessional.
In a criminal matter, a priest may encourage or require the penitent to surrender to authorities and may withhold absolution if the penitent refuses to do so. However, this is the extent of the leverage they wield. They may not directly or indirectly disclose the matter to civil authorities themselves (see priest-penitent privilege).
There are limited cases where portions of a confession may be revealed to others, but always with the penitent's permission and always without actually revealing the penitent's identity. This is the case, for example, with more serious offenses, as some excommunicable offenses are reserved to the bishop or even to the Holy See, and their permission to grant absolution must be obtained. In these cases, the priest hearing the confession asks the permission of the penitent to write a petition, using pseudonyms and containing the absolute minimum information necessary, to the bishop or to the Apostolic Penitentiary, the cardinal delegated by the Pope to handle such requests. This request may be forwarded, sealed, through the apostolic delegate or nuncio in a country (the Pope's ambassador), to be guarded by the privilege of a diplomatic pouch.