Canon 667. §1 In accordance with the institute’s own law, there is to be in all houses an enclosure appropriate to the character and mission of the institute. Some part of the house is always to be reserved to the members alone.

§2 A stricter discipline of enclosure is to be observed in monasteries which are devoted to the contemplative life.

§3 Monasteries of cloistered nuns who are wholly devoted to the contemplative life, must observe papal enclosure, that is, in accordance with the norms given by the
Apostolic See. Other monasteries of cloistered nuns are to observe an enclosure which is appropriate to their nature and is defined in the constitutions.

§4 The diocesan Bishop has the faculty of entering, for a just reason, the enclosure of cloistered nuns whose monasteries are situated in his diocese. For a grave reason and with the assent of the Abbess, he can permit others to be admitted to the enclosure, and permit the nuns to leave the enclosure for whatever time is truly necessary.

NB Congregation for Institutes of Consecrated life and Societies of Apostolic Life,
Instruction Cor Orans, 1 April 2018:

83. All female monasteries, without prejudice to internal autonomy and possible external exemption are subject to the diocesan Bishop, who exercises pastoral care in the following cases:
… g) the diocesan Bishop has the faculty, for a just cause, of entering the cloister and allowing other people to enter, with the consent of the Major Superior.
[Partial derogation from can. 667, §4 CJC approved by the Holy Father in a specific form.]

174. In derogation from the provision of can. 667, §4 CJC, the diocesan
Bishop, as well as the religious Ordinary, does not intervene in granting dispensation from the cloister.
[Exemption approved by the Holy Father in a specific form.]

175. In derogation of the provisions of can. 667, §4 CJC, the dispensation from the cloister rests solely with the Major Superior who, in the event that such dispensation exceeds fifteen days, can grant it only after having obtained the consent of her Council.
[Exemption approved by the Holy Father in a specific form.]