Catholic Encyclopedia, 1913:“The Pope himself, if notoriously guilty of heresy, would cease to be Pope because he would cease to be a member of the Church.”
Pope Innocent III:
“The Pope should not flatter himself about his power nor should he rashly glory in his honor and high estate, because the less he is judged by man, the more he is judged by God. Still the less can the Roman Pontiff glory because he can be judged by men, or rather, can be shown to be already judged, if for example he should wither away into heresy; because he who does not believe is already judged, In such a case it should be said of him: ‘If salt should lose its savor, it is good for nothing but to be cast out and trampled under foot by men.’”
St. Robert Bellarmine:
“A Pope who is a manifest heretic automatically ceases to be a Pope and head, just as he ceases automatically to be a Christian and a member of the Church. Wherefore, he can be judged and punished by the Church. This is the teaching of all the ancient Fathers who teach that manifest heretics immediately lose all jurisdiction.”
Saint Robert Bellarmine, De Rom. Pont., lib. II, cap. 30, 420
St. Alphonsus Liguori:
“If ever a Pope, as a private person, should fall into heresy, he should at once fall from the Pontificate. If, however, God were to permit a pope to become a notorious and contumacious heretic, he would by such fact cease to be pope, and the apostolic chair would be vacant.”
St. Francis de Sales:
“Now when the Pope is explicitly a heretic, he falls ipso facto from his dignity and out of the Church . . . ”
St. Antoninus:
“In the case in which the Pope would become a heretic, he would find himself, by that very fact alone and without any other sentence, separated from the Church. A head separated from a body cannot, as long as it remains separated, be head of the same body from which it was cut off.”
Pope Innocent III, Si Papa, 1198
“The Pope should not flatter himself about his power nor should he rashly glory in his honor and high estate, because the less he is judged by man, the more he is judged by God. Still the less can the Roman Pontiff glory because he can be judged by men, or rather, can be shown to be already judged, if for example he should wither away into heresy; because he who does not believe is already judged. In such a case it should be said of him: 'If salt should lose its savor, it is good for nothing but to be cast out and trampled under foot by men.’”
Billot, De Ecclesia, 1927:
“Given, therefore, the hypothesis of a pope who would become notoriously heretical, one must concede without hesitation that he would by that very fact lose the pontifical power, insofar as, having become an unbeliever, he would by his own will be cast outside the body of the Church.”
Wernz-Vidal, Canon Law, 1943:
“Through heresy notoriously and openly expressed, the Roman Pontiff, should he fall into such, is, by that very fact, and before any declaratory sentence of the Church, deprived of his power of jurisdiction.... a pope who falls into public heresy would by that fact cease to be a member of the Church; therefore he would also, upon that fact, cease to be the head of Church.…”
NOTE: Edward Peters, JD, JCD, Ref. Sig. Ap., in his blog A canonical primer on popes and heresy, December 16, 2016, offers the following comment on Wernz.
“I know of no author coming after Wernz who disputes this analysis.” See, e.g., Ayrinhac, CONSTITUTION (1930) 33; Sipos, ENCHIRIDION (1954) 156; Regatillo, INSTITUTIONES I (1961) 299; Palazzini, DMC III (1966) 573; and Wrenn (2001)…
A. Vermeersch, Epitome Iuris Canonici, 1949:
“At least according to the more common teaching; the Roman Pontiff as a private teacher can fall into manifest heresy. Then, without any declaratory sentence (for the Supreme See is judged by no one), he would automatically (ipso facto) fall from power which he who is no longer a member of the Church is unable to possess.”
Coronata, Institutiones Iuris Canonici, 1950:
“It cannot be proven however that the Roman Pontiff, as a private teacher, cannot become a heretic —If indeed such a situation would happen, he [the Roman Pontiff] would, by divine law, fall from office without any sentence, indeed, without even a declaratory one. He who openly professes heresy places himself outside the Church, and it is not likely that Christ would preserve the Primacy of His Church in one so unworthy. Wherefore, if the Roman Pontiff were to profess heresy, before any condemnatory sentence (which would be impossible anyway) he would lose his authority.”
Edward F. Regatillo, Institutiones Iuris Canonici, 1956:
“‘The pope loses office ipso facto because of public heresy.’ This is the more common teaching, because a pope would not be a member of the Church, and hence far less could he be its head.”
Marato, Institutiones Iuris Canonici, 1921:
“Heretics and schismatics are barred from the Supreme Pontificate by the Divine Law itself, because, although by divine law they are not considered incapable of participating in a certain type of ecclesiastical jurisdiction, nevertheless, they must certainly be regarded as excluded from occupying the throne of the Apostolic See, which is the infallible teacher of the truth of the faith and the center of ecclesiastical unity.”
Baldii, Institutiones Iuris Canonici, 1921:
“The law now in force for the election of the Roman Pontiff is reduced to these points:...Barred as incapable of being validly elected are the following: women, children who have not reached the age of reason, those suffering from habitual insanity, the unbaptized, heretics and schismatics....”
Wrenn, CLSA NEW COMM (2001) at 1618:
“Canon 1404 is not a statement of personal impeccability or inerrancy of the Holy Father. Should, indeed, the pope fall into heresy, it is understood that he would lose his office. To fall from Peter’s faith is to fall from his chair.”
Udalricus Beste, Introductio in Codicem, 1946
“Not a few canonists teach that, outside of death and abdication, the pontifical dignity can also be lost by falling into certain insanity, which is legally equivalent to death, as well as through manifest and notorious heresy. In the latter case, a pope would automatically fall from his power, and this indeed without the issuance of any sentence, for the first See (i.e., the See of Peter) is judged by no one ... The reason is that, by falling into heresy, the pope ceases to be a member of the Church. He who is not a member of a society, obviously, cannot be its head.”
Edward Peters, A Canonical Primer on Popes and Heresy, December 16, 2016:
As for the lack of detailed canonical examination of the mechanics for assessing possible papal heresy, Cocchi, COMMENTARIUM II/2 (1931) n. 155, ascribes it to the fact that law provides for common cases and adapts for rarer… In sum, and while additional important points could be offered on this matter, in the view of modern canonists from Wernz to Wrenn, however remote is the possibility of a pope actually falling into heresy and however difficult it might be to determine whether a pope has so fallen, such a catastrophe, Deus vetet, would result in the loss of papal office.