Separation from the monastic community can be a temporary one (such as absence, exclaustration) or a definitive severing of the canonical bonds with the community (such as dispensation from the vows or dismissal). In either case a spiritual bond should remain.
I: Temporary separation
A) Absences from the monastery 
To absent herself from the monastery, a nun needs the consent of her abbess and that of the Father Immediate or the Bishop (c. 667 § 4; Cst 13.3; Cst 29.2)  . This absence cannot be for more than three months  . In two cases, however, this three month limitation does not apply: for the treatment of illness and for study (c. 665 § 1)  . In these cases, even if nothing is explicitly mentioned in our legislation, the abbess must first obtain the consent of her council, as is required of an abbot in the same situation (Cst 13.3/m). Treatment of illness must be understood in a broad sense, including periods of psychotherapy.
The superior who gives a permission to live outside the monastery is always free to attach conditions to that permission. She may also withdraw the permission for a good reason.
The abbess, having listened to her council and with the consent of the Father Immediate or the Bishop, can permit a sister, in exceptional cases, to lead an eremitical life within the walls of the monastery. The hermit sister remains under the authority of the abbess (Cst 13.4).
If a sister manifests a vocation to the hermit life but, for diverse reasons, like the lack of space, it is not possible to live it within the walls of the monastery, it is possible to obtain an indult from the Holy See, so that she may live it outside. In these cases the Holy See asks that the abbess and her council be in agreement, as well as for an assurance that the abbess will continue to exercise pastoral care in regard to this hermit sister. It is also opportune to have the consent of the Bishop of the diocese where the sister will live. The indult that the Holy See gives in such cases is not an indult of exclaustration or of absence, but simply a dispensation from the restrictive clause "within the walls of the monastery" of Cst 13.4. However, a nun or her abbess may have reason explicitly to ask for an indult of exclaustration.
B) Imposed transfer to another monastery
The Abbot General can oblige a sister to transfer temporarily to another monastery under very specific conditions:
a) "for the sake of peace" (pacis causa); which does not necessarily imply any fault on the part of the nun asked to leave. This is, therefore, to be considered an administrative act, and not a judiciary or punitive one;
b) at the request of the abbess with the consent of her council;
c) after hearing the sister in question;
d) with the consent of the Father Immediate;
e) with the consent of the Permanent Council;
f) this imposed transfer cannot be imposed for more than five years;
g) due consideration must be given to the community that receives the sister (St 60.B).
Only the Holy See can grant an indult of exclaustration to nuns (c. 686 § 2; Cst 62.1)  . The request of the nun is usually sent to the Abbot General by the abbess with her opinion and that of her council. It is then presented to the Holy See by the Procurator General along with the opinion of the Abbot General and his council  .
For a grave cause, equity and charity being maintained, an abbess, with the consent of her council, may ask the Abbot General to request the Holy See to impose an exclaustration on a nun. The Abbot General needs the consent of his own council, and the Father Immediate must also be consulted (c. 686 § 3; St 62.1.A)  .
Situation of the exclaustrated nun
An exclaustrated nun is released from those obligations that are incompatible with her new state of life. However, she remains dependent on her abbess and under her care. She is also dependent on the Ordinary of the place. She can wear the habit of the Order, unless it is stated otherwise in the indult, but she loses both active and passive voice (c. 687; Cst 36.3; Cst 62.2).
If an abbess has good reasons to ask that some specific conditions be attached to an indult of exclaustration, she should mention it at the time the request is presented. Once the indult is granted by a higher authority, a lower one cannot attach conditions to it  .
A nun who has requested an indult of exclaustration is free to use it or not (except in the case of an imposed exclaustration). If she uses it, she is free to return to the monastery before the end of the period for which the indult was given.
D) Loss of active and passive voice
The exercise of the active and passive voice as member of the conventual chapter is suspended when a sister has been away from her monastery for more than six months (St 36.3.B). This applies to all the forms of absence mentioned above. Exceptions to this rule are:
a) those who are at the service of the Order;
b) those who are absent for reasons of study or health;
Although those belonging to these three categories keep their active and passive voice, they should exercise prudence and discernment in deciding whether to use this right or not (St 36.3.A).
When the sister who has been away for more than six months decides to return definitively to the monastery, the abbess, with the consent of her council and taking into consideration the duration of the absence, can require that the sister live in the community for a certain period before resuming the exercise of her voting rights (St 36.3.B.a). This applies to someone returning from a period of exclaustration as well as to someone who has been away with a permission of absence.
At the time of an election, in the case of a sister who has lost her voting rights because of a prolonged absence, and has returned to the monastery on a permanent basis (habitualiter commoranti in monasterio), but has not yet been given back the exercise of her voting rights in the conventual chapter, the president of the election can restore her voting rights for that election, after consulting the conventual chapter (St 36.3.B.b). This would not apply to someone who would temporarily return to the monastery only for the election.
Because of this loss of active and passive voting rights by those who are absent from the monastery, there is very little difference in practice, for members of our Order, between someone who has a permission of "absence" and someone who has an "exclaustration". The exclaustrated nun loses her voting rights at the moment of her exclaustration, while the absent one loses them after six months.
II: Definitive separation
The novice is free to leave at any time during her novitiate or at the end of it (c. 653 § 1).
The abbess may dismiss her during the novitiate (c. 653 § 1). At the end of the novitiate, if she is judged suitable, she must be accepted. Otherwise she must be dismissed. If a doubt exists concerning suitability, the time of probation may be prolonged by the abbess, but for a period not exceeding six months (c. 653 § 2)  . Although no canonical process is foreseen for such a dismissal, it is assumed that the superior will act with a keen sense of justice and charity. If the novice feels that she has been unjustly treated, she may have recourse to higher superiors, but her recourse does not suspend the application of the decision.
B) Temporary professed
One who, for a grave cause, asks to leave the monastery during the time of temporary profession can obtain an indult to leave from the Abbot General with the consent of his council (c. 688 § 2; Cst 63.1; St 84.1.C.j). The Abbot General will not normally grant such an indult before at least hearing the opinion of the abbess and her council.
At the end of the period for which the temporary vows have been made, the nun is free to leave (c. 688 § 1)  . If her vows were made for a year at a time, the temporary professed must be accepted to renewing them if she asks for it and if she is judged suitable (idonea) (c. 657 § 1). At the end of her three years of temporary profession, likewise, she must be accepted to solemn profession if she asks to make it and if she is judged suitable (idonea) (c. 689 § 1). The abbess must hear her council before excluding a nun either from renewing her temporary profession or from making solemn profession at the end of her temporary vows (St 38.C.e; Cst 63.2). Such an exclusion for a just cause should not be confused with "dismissal"; it does not imply any fault on the part of the professed nun. The nun who is excluded from further profession should, however, be given the reasons for this exclusion, at least in a general manner.
If a nun in temporary vows contracts a physical or psychological illness the abbess is to observe canon 689 § 2-3 of the CIC, which say:
§ 2. Even if it is contracted after profession, physical or psychic illness which in the judgment of experts renders the [temporary professed who has arrived at the end of her vows] unsuited to lead the life of the institute, constitutes a reason for not admitting such a person to a renewal of profession or to making perpetual profession, unless the infirmity had been incurred through the institute's negligence or through work performed in the institute.
§ 3. A religious, however, who becomes insane during temporary vows, even though unable to make a new profession, cannot be dismissed from the institute.
C) Change of Stability 
A nun is definitively separated from her community when she makes her stability in another monastery of the Order. A grave cause is required to do so. Furthermore, the consent of the abbesses of both monasteries is required and that of the conventual chapter of the monastery that receives her.
In the case of a nun who has made her stability in a new foundation when this became autonomous, the consent of the conventual chapter is not required to return to the monastery of her first profession; but she still needs the permission of the abbesses of both monasteries (Cst 60).
A nun who left the community of her profession to exercise
the abbatial ministry in another community of the Order can, within
two months a year of resigning from office or completing her mandate,
resume her first stability (St 40.C). In this case no consent of the abbess
of either monastery or of the conventual chapter is required.
D) Transitus to another Institute
If a nun in solemn vows wishes to transfer to another religious institute she needs the permission of the Abbot General and that of the Superioress General of the Institute to which she wants to transfer, each with the consent of their council (c. 684 § 1; Cst 61; St 84.1.C.g). To transfer to a secular institute or to a society of apostolic life, the permission of the Holy See is needed and its instructions are to be followed (c. 684 § 5).
Normally, she will live for a certain time in the community to which she wants to transfer, before starting her period of probation. For this she will need a permission of absence that her abbess can give her, with the consent either of the Father Immediate or the Bishop. The length of the period of probation is determined by the proper law of the other Institute, but must be at least three years (c. 684 § 2).
During her time of probation she still has her vows in her monastic community, but her rights and obligations in it are suspended. From the beginning of probation, however, she is bound to observe the laws of the new institute. By profession in the new institute she is incorporated into it, and the earlier vows, rights and obligations cease (c. 685 § 1-2). If she is not accepted to profession, even after a long period of probation, she simply returns to her former community with all her rights and obligations. Nevertheless, since she has been away for more than six months, the abbess may request her to live in the community for a certain period before resuming the exercise of her voting rights, as explained above.
E) Dispensation from solemn vows
A dispensation from solemn vows can be granted only by the Holy See (c. 691 § 2). A nun will not request such an indult except for very grave causes, weighed before God (c. 691 § 1).
A written request signed by the nun herself is required in which she gives, at least succinctly, the reasons. It is not enough for her abbess to say that the nun agrees or that she has made a verbal request. The Holy See will not ordinarily grant the indult without having this request signed by the nun herself. In that document the nun should normally address herself to the Holy Father; but letters written to the abbess or to the Abbot General are also accepted.
The nun will give this written request to her abbess, who will discuss it with her council. The abbess will then forward the request to the Abbot General with her opinion. The Abbot General will discuss it with his own council, and then forward the request to the Holy See with his own opinion and that of his council (c. 691 § 1; Cst 64; St 38.C.f). It should be noted that the nun's abbess and the Abbot General are not free not to pass on the request to the Holy See. What is requested from them is their opinion and that of their respective councils. This should be done very seriously, because the Holy See will make its decision to grant the dispensation or not, largely on the basis of these opinions and recommendations.
When an indult of dispensation from monastic vows is given by the Holy See, it is sent to the abbess who has the responsibility to communicate it to the nun. If a nun has changed her mind in the meantime, she is still free to refuse the indult that has been granted to her; but unless she rejects it in the act of notification, it becomes immediately effective (c. 692). There is no need for the nun to "sign" the indult she has received  .
It is the responsibility of the abbess to inform the parish priest of the prarish where the professed sister was baptized that she has received a dispense from her vows.
The most radical way of being separated from the monastic community consists in the dismissal from it.
a) In some situations a nun is ipso facto dismissed from her community and from the Order. These are when someone
- has notoriously abandoned the Catholic faith;
- has contracted marriage or has attempted it even only civilly  .
In these cases the abbess with her council must, after collecting the evidence, without delay make a declaration of the fact, so that the dismissal is juridically established. One must note that the nun, in this case, is not "dismissed" by the abbess and her council, since the dismissal was an automatic consequence of her own action (c. 694 § 1-2).  .
b) In other situations a nun either must or may be dismissed.
The cases in which a nun must be dismissed are given in canons 695 § 1, 1395, 1397 and 1398. However, in the cases mentioned in c. 1395 § 2, the dismissal can be avoided if "the superior judges that dismissal is not entirely necessary and that the correction of the member and restitution of justice and reparation of scandal can be sufficiently assured in some other way" (c. 695 § 1).
A nun may be dismissed for other causes, provided that they are grave, external, imputable and juridically proven, such as habitual neglect of the obligations of consecrated life; repeated violations of the sacred bonds; pertinacious disobedience to lawful prescriptions of superiors in a serious matter, grave scandal arising from culpable behavior; ... unlawful absence from the monastery lasting six months; etc. (see c. 696 § 1-2).
In all these cases of dismissal a very complex procedure that has been devised in order to protect all the rights of the religious, must be followed (canons 694-704). If an abbess, unfortunately, has a situation for which a dismissal seems the only solution, she will be well advised to request the help of a good canonist unless she is one herself. Here is, briefly, the procedure that needs to be followed  :
aa) The abbess must hear her council before beginning the process of dismissal of a nun in solemn or temporary vows (c. 697; St 38.C.g; Cst 65; St 84.1.E).
bb) The abbess will collect the proofs (c. 697 § 1), do the various monitions required by the law (c. 697 § 2), and transmit all the acts and documents to the Abbot General (c. 697 § 3). The nun threatened with dismissal must be given ample opportunity for explaining and defending herself and for direct recourse to the Abbot General (c. 697 § 2; c. 698).
cc) The Abbot General, acting collegially with his four councilors, will proceed to the careful weighing of the proofs, arguments and defenses. If it has been so decided by a secret ballot, the Abbot General will issue the decree of dismissal (c. 699 § 1)l  .
dd) The decree is transmitted to the Holy See with all the acts for confirmation. The dismissed nun has the right to recourse within ten days from receiving the notification. The recourse has a suspensive effect (c. 700).
ee) By lawful dismissal, both the vows and the rights and duties deriving from profession automatically cease (c. 701).
G) Obligations toward those who leave
The abbess continues to manifest a pastoral care to those who leave the monastery. Most of all, she will act in a disinterested manner, keeping in mind the good of the one who leaves as well as that of the community.
Those who leave the community or are dismissed, are not entitled to claim anything from the monastery for services rendered. Nevertheless, the abbess is to observe the norms of equity and evangelical charity towards members who depart (c. 702; Cst 59.2).
In order to preserve the good of the one who leaves as well as that of the community the abbess will need to have a sound knowledge of the social legislation of the place where the monastery is located (c. 702; Cst 59.1.2; St 59.2.A).
The amount of material help given to someone departing will obviously depend on many factors:
- the time spent in community;
- the age, education, and capacity to find a job;
- the economic and social structure of the country.
 Constitution 29 says: "Regarding the exits of the sisters from the cloister...the norms of universal law are followed". It's a question of the norms given in Venite seorsum, but remember that many points of Venite seorsum have been modified by the new code of canon law, by other documents of the Holy See, such as the Instruction of 1990 on Formation, and our own Constitutions.
 In our Order the Father Immediate has the same rights that the Bishop has to give permission to the nuns to leave the enclosure (Cst 13.3) If the consent of the Father Immediate is obtained, that of the Bishop is not necessary; and vice versa. It is advisable to inform the local Bishop of this particular feature of our law. In most of these cases either the Father Immediate or the Bishop will have given the abbess a very general authorization. However, it is important to note that neither the Father Immediate nor the Bishop can give this permission without the consent of the abbess.
 The three month limit is that established by Venite seorsum, norm 7,d.
 The Bishop or the Father Immediate, taking into account cc. 667 § 4 and 665 § 1, may give to a nun a permission of absence for as long as necessary, without a limit of time, for reasons of health and studies. In this case, it is really a permission of absence and not an exclaustration, which is always reserved to the Holy See. (Cf. Jesús TORRES, C.M.F., "L'assenza dalla casa religiosa" Informationes SCRIS 1993, pp. 103-104).
 In some situations, as in the case of a nun who needs to go out in order to take care of her parents, the Holy See tends to give a "permission of absence" rather than an "indult of exclaustration", unless an exclaustration is explicitly asked for.
 In the presentation of the request to the Holy See the Procurator General usually includes the letter of the nun to the Abbot General, the letter of the local abbess and any documents (e.g. a report from a psychotherapist). For this reason, it is recommended that each one of these documents be dedicated only to the request in question and not deal with this request among many other topics. If an abbess has two requests of exclaustration to present at the same time, she should write two letters rather than deal with both in the same letter.
 The most common situation in which the Holy See accepts to impose an exclaustration is when a religious, because of psychological problems (e.g. schizophrenia, paranoia) has become very disruptive in the life of the community but does not accept to go away for treatment.
 For example, according to Canon Law (c. 687) an exclaustrated nun has the right to wear her monastic habit. The abbess cannot prevent her from doing it unless it was mentioned explicitly in the indult.
 We deal here only with separation from the community. All that concerns admission (or re-admission) to profession is treated in a more elaborate manner in another section of the vademecum.
 If someone feels the need to go away for a time of reflection, she may be informed of the possibility of being reaccepted later on without the obligation of doing another novitiate (c. 690; Cst 66).
 The change of stability, in this section, as well as the transitus to another Institute, in the next section, are treated in this document from the point of view of the community "a qua", that is, the community from which someone departs.
 It happened that nuns, who had been duly dispensed from their vows, said that they were still members of their communities because they had not "signed" the indult. They were in fact definitively separated from their community at the time the dispensation was made known to them, if they did not reject it then.
 Someone who lives in concubinage, without contracting marriage, is not ipso facto dismissed; but she must be dismissed (c. 695; c. 1395 § 1).
 Evidently, it would make no sense in these cases to ask for a dispensation from vows, since the nun was ipso facto dismissed from the Order either at the time she contracted a civil marriage or abandoned the Catholic faith.
 This is only a very sketchy summary. A very detailed procedure has to be followed in order to assure the fairness of the process and for the dismissal to be confirmed by the Holy See.
 It must be noted that the nun is dismissed not by the Holy See but by the Order, although the confirmation by the Holy See of the decree of dismissal is required.