On departure from a religious [institute]
Canon 637
One professed by temporary vows, upon the completion of the time of the vows, is able freely to [leave] a religious [institute]; likewise the religious [institute] for just and reasonable causes can exclude one from the renewal of temporary vows or from giving perpetual profession, but not, however, because of infirmity, unless it has been certainly proved that this was intentionally withheld or simulated prior to profession.
Canon 638
An indult of staying outside the cloister, whether temporary, in which case it is an indult of exclaustration, or perpetual, in which case it is an indult of secularization, can only be given by the Apostolic See in a religious [institute] of pontifical right; in a religious [institute] of diocesan right [it can also be given by] the local Ordinary.
Canon 639
Whoever seeks an indult of exclaustration from the Apostolic See remains bound by the vows and other obligations of his profession that can be reconciled with his state; nevertheless, he must not wear outside [the institute] the habit or style of the religious [institute]; during the period of the indult, one lacks active and passive voice but enjoys the merely spiritual privileges of his religious [institute], and is under the Ordinary of the place where he is by reason of the vow of obedience, in place of the Superior of his own religious [institute].
Canon 640
§ 1. One who has obtained an indult of secularization and leaves the religious [institute]:
1.° Is separated from the religious [institute], must put off the exterior habit or style, and in Mass and in the canonical hours and in the use and dispensation of Sacraments is considered a secular;
2.° He remains freed from vows, [but not from] the burdens attached to major orders if he was in sacred [orders]; he is not bound by the obligation of reciting the canonical hours in view of profession, nor is he bound by the other rules and constitutions.
§ 2. If by apostolic indult he is once again received into a religious [institute], he shall undergo novitiate and profession and obtain a place among the professed from the day of the new profession.
Canon 641
§ 1. If a religious constituted in sacred [orders] has not lost his own diocese according to the norm of Canon 585, he must, not having renewed his vows or having obtained an indult of secularization, return to his own diocese and be received by his own Ordinary; if he has lost it, he cannot exercise sacred orders outside the religious [institute] until he finds reception by a benevolent Bishop or until the Apostolic See provides otherwise.
§ 2. A Bishop can receive a religious either purely and simply or for an experimental [period] of three years: in the first case the religious is by that [fact] incardinated into the diocese; in the second the Bishop can demand a time of probation but not beyond another three years; the which [time] having passed, the religious, unless he has been dismissed beforehand, is by that fact incardinated into the diocese.
Canon 642
§ 1. Any professed having returned to the world is still able according to the norm of Canon 641 to exercise sacred orders, but they are nevertheless prohibited without a new and special indult of the Holy See [from having]:
1.° Any benefice in a major or minor basilica and in a cathedral church;
2.° Any teaching [post] and office in a major or minor Seminary or college in which clerics are educated and likewise in Universities and Institutes that enjoy the conferral of academic degrees by apostolic privilege;
3.° Any office or duty in an episcopal Curia and in religious houses of men or women even if it concerns a diocesan Congregation.
§ 2. These things apply even for those who gave temporary vows or an oath of perseverance or certain special promises according to the norm of the constitutions and were dispensed from them if for six complete years they were bound by them.
Canon 643
§ 1. Whoever leaves a religious [institute] at the completion of temporary vows or who has obtained an indult of secularization or who was dismissed from it can seek nothing for any works done on behalf of the religious [institute].
§ 2. If, however, a religious woman was received without a dowry [and] she is not able to provide for herself out of her own goods, the religious [institute] out of charity must give to her what is required for a safe and becoming return home and so provide [for her] for a period of time observing natural equity by mutual consent or in the case of disagreement to be determined by the local Ordinary so that she can live honestly.
Canon 644
§ 1. One professed by perpetual vows, whether solemn or simple, who has illegitimately left from the religious house without the intention of returning or who has legitimately left but has ceased his religious obedience and who is not returning, is called an apostate from a religious [institute].
§ 2. This evil will mentioned in § 1 is presumed in law if a religious has not returned within one month or manifested to the Superior the intention of returning.
§ 3. A fugitive is one who without the permission of the Superiors leaves the religious house with the intention of returning to the religious [institute].
Canon 645
§ 1. An apostate and a fugitive are not absolved of the obligation of the rule and vows and must return without delay to the religious [institute].
§ 2. Superiors must inquire after them solicitously and receive them if they return with an act of true penitence; the local Ordinary shall take care cautiously for the return of apostate or fugitive nuns, and, if it concerns an exempt monastery, the regular Superior [shall do so also].