As an aside, someone emailed me that Chapter 21 had been translated into English on Scribd, but I don't have a membership.  They give a 1-page free teaser (slightly improved by me), which will give you an idea of the subject matter discussed in the book:


Do Adrien Gréa
–

The Church and its Divine Constitution

Chapter XXI
The extraordinary act of the episcopate


Of what it consists

The power of the episcopate in the government of the universal Church exercises itself in an ordinary way through the councils and through the less splendorous assistance which the dispersed bishops, always united in the dependence and under the impulse of their head, give without ceasing for the maintenance of the faith and of discipline.

But this power of the episcopate has also had in history extraordinary manifestations of which it is important to be brought back to the same subordination and to be submitted to the same essential laws of the hierarchy.

We want to speak here primarily of the authority deployed by the apostles, their disciples, and the bishops of the first times, their successors, to announce everywhere the Gospel and establish the Church, and secondarily of the extraordinary actions by which, subsequently, one saw bishops not hesitate to remedy the pressing necessities of the Christian people and to lift up again, by the use of a power quasi apostolic, Churches brought into extreme peril by the infidels and the heretics.

These facts have been abused to pull out of proportion the authority of the bishops and to give them a sort of primitive and independent sovereignty.

It is thus necessary to overthrow this fundament of error. We will do so in simply recalling the doctrine exposed in our second part, principally in chapter 8, where we have treated of the relations of essential dependence that unite the particular Churches to the universal Church, and in bringing back these facts to the laws already known of the hierarchy, laws which, everywhere and always, establish the complete subordination of the bishops to their head.

And first, it is good to recall that the universal Church, preceding in everything the particular Churches, possesses before these and guards always sovereignly the mission of preaching the Gospel everywhere and of saving souls.

It follows from there that the hierarchy of the universal Church, who is not deprived of her immediate authority over souls even by the establishment of particular Churches, remains alone charged with the salvation of men when these are defunct, and deploys her powers to assure them this benefit.

This hierarchy is that of the Pope and the bishops. It is to the Pope that belongs the sovereign and principal action. But the bishops themselves, since they are associated with him as ministers of the universal Church, are called to take part in it. They appear thus vested with a power which is not carried out on their particular flocks and which exercises itself in places where there are not yet founded particular Churches and titular bishops established, and in those where the local hierarchies, having been established, are harmed in their existence or struck with impotence. 

[This final bolded sentence gets to the heart of the matter surrounding the legitimacy/illegitimacy of Archbishop Lefebvre's episcopal consecrations, and translating Grea's doctrine surrounding this point is my primary interest in the undertaking -SJ]

Bookdepository.com is always worth a look for classic facsimile reprints:
Results for Dom adrien grea l'eglise et sa constitution divine | Book Depository

I don't know much about the specifics of supplied jurisdiction and such, only that it is necessary to act in accord with the reasonably presumed will of the legitimate authority  when the authority is absent (epikeia).  And obviously if the authority is present it is necessary to submit to it as long as a higher authority does not forbid it.

Hello SID-

What you say regarding epikeia is true in what Dom Grea calls the narrow or improper sense, but not in the broad/proper sense (his words).

I have an article in mind which I’m trying to dig up, and will post it shortly.

Meanwhile, some thoughts regarding the REASONABLE will of the pope, which I once wrote elsewhere:

Pacelli [a username, not Pius XII -SJ] seems to place much emphasis on the will of the Pope.

I'm not sure that consideration is relevant.

When the salvation of souls is at stake, the consent of the Pope is owed; it is not within the Pope's power to withhold it.

Some relevant quotes from an article on the 1988 episcopal consecrations: http://www.sspxasia.com/Docuмents/SiSiNoNo/1999_September/The_1988_Consecrations.htm

"This is not, in fact, the case of authority not being bound to oblige because "summum ius summa iniuria," or one which issues an inopportune command lacking in prudence, but which nevertheless people could be bound to obey all the same in view of the common good. This is, on the other hand, the case of authority that cannot oblige, because its command is opposed to a precept of divine and natural law "more grave and obliging."8 In such a case to obey the law or the legislator would be "evil and a sin" (Suarez, De Legibus, L. VI, c. VII, n.. St. Thomas calls obedience in such a case "evil" (SI; 11-11, Q120, A.1). Cajetan refers to it as a "vice" (Cajetan in 1.2, q.96, a.6). Hence, refusal to obey becomes a duty (i.e" inoboedientia debita).9"

...


"Therefore, the command or prohibition of a superior which, by reason of extraordinary circuмstances, results in harm to souls and the common good, as well as being contrary to the state of the subject (cf. Suarez, De religione, LX, cap.IX, n.4), loses its character of lawfulness and absolves the subject from his duty to obey, "...nor are those who behave in such a way, to be accused of having failed in obedience, because if the will of leaders is repugnant to the will and the laws of God, these leaders exceed the measure of their power.14"

...

"In his Dictionary of Canon Law, Naz writes that of St. Thomas Aquinas:

…the coming into play of epikeia is subordinate to the existence of a right. In fact, in certain cases, the law loses its power to bind – as where its application would be contrary to the common good or to natural law – and in such a case it is not in the power of the legislator to bind or to oblige.19"

...

"Regarding seeking permissions from the superior, Suarez explains (speaking precisely of the pope) that here, “it is not a question of interpreting the will of the superior, but [a question] of his power” in order to know what is not necessary to ask the superior, because it is permitted to make use of “doctrinal rules” or “principles of theology and law,”22 given that “one knows with more certitude the power [of the superior] which is not free, rather than his will, which is free [emphasis added].”23 For that reason the subject, having prudently examined the circuмstances and been informed by the “doctrinal rules” or by the “principles of theology and law” that is “beyond the power of legislator”24 to bind anyone to respect the law when it causes grave harm to so many souls, and that to obey in such a case would be “evil and a sin,”25 he may not - indeed, he must not - submit to the law or to the command“on his own authority,”26 “by his own judgment.”27 Hence, by his own initiative, he refuses submission “without recourse to the superior,”28 that is to say, without any dispensation or approval on the part of the said superior. The reason, writes Suarez, is: that in such a case the authority of the superior cannot have any effect; indeed, even if he were to will that the subject, after having had recourse to him, should observe the law, the latter would not be able to obey him because he must obey God rather than man and hence in such a case its is out of place (“impertinens”) to ask for permission.29"

Conclusion:

1) The consent of the Pope is owed;
2) The Pope has no power to withhold consent;
3) Even if he did, it would not be possible to obey him;
4) And in such a situation, it is out of place even to seek to ascertain the Pope's will, since the course of action is necessary regardless.

Consequently, seeking to ascertain the will of the Pope is irrelevant (or stated differently, his consent is given regardless of any stated opposition, since such opposition would exceed the measure of his power).