Drawing upon the text of Lumen Gentium, the Catechism reminds us that the office of bishop is lifelong and requires the exercise of office in a manner which ought to 'edify the spirit of service' (cf CCC 861 & 893). Similarly, the Code of Canon Law 1983 defines an 'ecclesiastical office' as a function enjoying two characteristics: a) stability; and b) a spiritual purpose (canon 145). Thus, having declared that the power of governance is exercisable in the external forum only (canon 130) the legislator confirms that the end to which the exercise of the munus regendi is directed must be a spiritual purpose. This is, of course, entirely consistent with the primary objective to which the entirety of the Church (and her laws) is directed: the salvation of souls.
In this context, stability should not be equated with rigidity; but instead a quality of order and predictability. After all, the Church and those who participate in the exercise of governance, are collaborators in a single endeavour. The means by which the Church directs its efforts in this regard is through the cultivation and protection of human relationships. It is doubtless for this reason that the Code of Canon law lays heavy emphasis upon the duty to ensure due consideration is given to the care of souls in the timing of appointment to (and duration of) ecclesiastical offices (e.g. canon 151). Nor is the Code silent as to the position of the appointee. In this respect, canon 184 §1 is informative; identifying the means by which ecclesiastical office may be lost. As one might expect, these include effluxion of time, attainment of the designated age and/or removal or privation. Canon 186 provides:
"Loss of an office by the lapse of a predetermined time or by the reaching of a certain age takes effect only from the moment when the competent authority communicates it in writing."
It is to be borne in mind that this stability - which represents a core component of this aspect of the Code- is only underscored when one has regard to the norms concerning transfer (canon 190) and removal from office (canon 192 et seq).
It may be said that in both constitutional and pastoral terms, the particular Church is heavily dependent upon the preservation of stability in the conferral, and appointment to office, of both the Diocesan Bishop and local pastors. In each case, the law "requests" the office holder to tender his resignation upon attainment of the normal retirement age (see canons 401 §1 and 538 §3). It follows, that such request may be denied or deferred.
The Holy Father's motu proprio "Imparare a congedarsi" (12 February 2018) has been reported as having the effect of "allowing" Vatican Bishops to serve beyond the age of 75 (e.g. https://www.ncronline.org/news/vatican). However, this may not be quite accurate. The text of this short document (available in Italian at http://w2.vatican.va/content/francesco/it/motu_proprio) speaks of those attaining their 75 year as being 'invited to renounce" (invitati a presentare al Sommo Pontefice la rinuncia al loro ufficio pastorale) (art 1). In addition, those who reach the designated age whilst serving within dicastories, do not on account of their age cease to hold office (non cessano ipso facto dal loro ufficio) but must (devono) submit their resignation. These provisions may be said to introduce an element of consistency between such office holders, pastors and Diocesan Bishops; with a like discretion being invested in the Supreme Pontiff as to when/how any resignation should take effect (see Art 4). Read in this way, the motu proprio appears to be more in the manner of "reste un poco".
There will be those who seek to depict this latest document from the Holy Father as sinister; viewing it as evidence of a desire for closer personal control over the various dicastories. It is not easy to reconcile this perception with the fact that maintaining the status quo would have enabled the Holy Father to exercise more control in the nomination/replacement of substitute candidates.
If the Holy Father's ambition is and remains to secure effective continuity for the better service of the mission of the Church, one wonders how he might respond to those episcopal practices by which priests (who are de facto pastors of parishes) have been denied the stability of their proper office and instead been required to discharge the role of "priests in residence". We can only hope that the motu proprio will prompt reconsideration of such practices; which undermine both the priests concerned and the office they seek to discharge.