Canon 638. §1 It is for an institute’s own law, within the limits of the universal law, to define the acts which exceed the purpose and the manner of ordinary administration, and to establish what is needed for the validity of an act of extraordinary administration.

§2 Besides Superiors, other officials designated for this task in the institute’s own law may, within the limits of their office, validly make payments and perform juridical acts of ordinary administration.

§3 For the validity of alienation, and of any transaction by which the patrimonial condition of the juridical person could be adversely affected there is required the written permission of the competent Superior, given with the consent of his or her council. Moreover, the permission of the Holy See is required if the transaction involves a sum exceeding that which the Holy See has determined for each region, or if it concerns things donated to the Church as a result of a vow, or objects which are precious by reason of their artistic or historical value.

§4 For the autonomous monasteries mentioned in can. 615, and for institutes of diocesan right, the written consent of the diocesan Bishop is necessary.

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

52. In derogation from can. 638, §4 CJC, for the validity of the alienation and of any other transaction by which the patrimonial situation of the monastery could be damaged, the written permission of the Major Superior is required with the consent of the Council or of the conventual Chapter, depending on the value of the sale and the transaction, and the opinion of the Federal President.
[Exemption approved by the Holy Father in a specific form.]

81. As regards the female monasteries entrusted to the particular vigilance of the diocesan Bishop, this is expressed in respect to the monastery community mainly in the cases established by the universal law; as the diocesan Bishop, he:
… d) in derogation from can. 638, §4 CJC, gives as Local Ordinary, his written consent for particular administrative acts, if established by its proper law.
[Exemption approved by the Holy Father in a specific form.]

108. In derogation from can. 638, §4 CJC, for the validity of the alienation of the assets of the suppressed monasteries, the President of the Federation and the Federal Council, beyond the value of the asset to be alienated, always and exclusively requires written permission from the Holy See.
[Exemption approved by the Holy Father in a specific form.]