Let's compare the quote provided by PaxChristi2 (Siscoe) with the same quote provided by Don Paolo (without any the ellipses):
Here's two. I posted the first one previously. It is from the former rector of the Gregorian, who not only taught canon law for most of his adult life, but is one of the relatively few that has studied the past 1000 years of canonical tradition on the subject.
Quote
Father Ghirlanda, S.J., (2013): “The vacancy of the Roman See occurs in case of the cessation of the office on the part of the Roman Pontiff, which happens for four reasons: 1) Death, 2) Sure and perpetual insanity or complete mental infirmity; 3) Notorious apostasy, heresy, schism; 4) Resignation. In the first case, the Apostolic See is vacant from the moment of death of the Roman Pontiff; in the second and in the third from the moment of the declaration on the part of the cardinals; in the fourth from the moment of the renunciation." (…) There is the case, admitted by doctrine, of notorious apostasy, heresy and schism, into which the Roman Pontiff could fall, but as a ‘private doctor,’ that does not demand the assent of the faithful (…) However, in such cases, because ‘the first see is judged by no one’ (Canon 1404) no one could depose the Roman Pontiff, but only a declaration of the fact would be had, which would have to be done by the Cardinals, at least of those present in Rome.” ("La Civiltà Cattolica" March, 2, 2013)
The Church judges and declares the fact, and at that "moment" the See becomes vacant.
versus
It is being claimed by some that the Canon Law professor and former rector of the Pontifical Gregorian University, Fr. Giancarlo Ghirlanda SJ, says that a notorious heretic pope would not cease to be pope until he is declared a heretic by the cardinals. That is not his position. His position on the question is identical to my own:
Cessation from the office of the Roman Pontiff
Excerpt from Quaderno n. 3905 del 2 marzo 2013 de "La Civiltà Cattolica", pp. 445-462.
Then, if the Roman Pontiff did not express what is already contained in the Church, he would no longer be in communion with the whole Church, and therefore with the other Bishops, successors of the Apostles. The communion of the Roman Pontiff with the Church and with the Bishops, according to Vatican I (3), cannot be proven by the consent of the Church and the Bishops, as it would no longer be a full and supreme power freely exercised (c. 331; "Nota Explicativa Praevia" 4). The criterion then is the protection of ecclesial communion itself. There where this no longer existed on the part of the Pope, he would no longer have any power, because ipso iure would fall from his primatial office. This is the case, admitted in doctrine, of the notorious apostasy, heresy and schism, in which the Roman Pontiff could fall, but as a "private doctor", who does not commit the assent of the faithful, because by faith in the personal infallibility that the Roman Pontiff has in the performance of his office, and therefore in the assistance of the Holy Spirit, we must say that he cannot make heretical statements wanting to commit his primatial authority, because, if he did so, he would fall ipso jure from his office. However in such cases, since "the first seat is not judged by anyone" (c. 1404), no one could depose the Roman Pontiff, but there would only be a declaration of the fact, which should be on the part of the Cardinals, at least of those present in Rome. This eventuality, however, although foreseen in the doctrine, is considered totally improbable by intervention of the Divine Providence in favor of the Church (4).
FOOTNOTES 3. Constitution, Pastor Aeternus, chapter 4, Denzinger-Schonmetzer 3074. 4. Cf. F. J. Wernz. P. Vida., “Ius canonicuм”, tome II, “De Personis”, Rome, 1933, 517 seqq.
Don Paolo even gives us a link to the entire text: http://chiesa.espresso.repubblica.it/articolo/1350455.html
That's some crafty editing by PaxChristi2 (Siscoe). I wonder how he sleeps at night?