“Further, if ever it should appear that any bishop (even one acting as an archbishop, patriarch or primate), or a cardinal of the Roman Church, or a legate (as mentioned above), or even the Roman Pontiff (whether prior to his promotion to cardinal, or prior to his election as Roman Pontiff), has beforehand deviated from the Catholic faith or fallen into any heresy, We enact, decree, determine and define:
— “Such promotion or election in and of itself, even with the agreement and unanimous consent of all the cardinals, shall be null, legally invalid and void.
— “It shall not be possible for such a promotion or election to be deemed valid or to be valid, neither through reception of office, consecration, subsequent administration, or possession, nor even through the putative enthronement of a Roman Pontiff himself, together with the veneration and obedience accorded him by all.
— “Such promotion or election, shall not through any lapse of tune in the foregoing situation, be considered even partially legitimate in any way . . .
— “Each and all of the words, as acts, laws, appointments of those so promoted or elected —and indeed, whatsoever flows therefrom — shall be lacking in force, and shall grant no stability and legal power to anyone whatsoever.
— “Those so promoted or elected, by that very fact and without the need to make any further declaration, shall be deprived of any dignity, position, honor, title, authority, office and power.”

“Appointment to the Office of the Primacy.
1. What is required by divine law for this appointment . . . Also required for validity is that the one elected be a member of the Church; hence, heretics and apostates (at least public ones) are excluded. . . ”
“It cannot be proven however that the Roman Pontiff, as a private teacher, cannot become a heretic — if, for example, he would contumaciously deny a previously defined dogma. Such impeccability was never promised by God. Indeed, Pope Innocent III expressly admits such a case is possible.
“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.”

“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.”

“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.”

All former disciplinary laws which were in force until now, and are neither explicitly nor implicitly contained in the Code, shall be regarded as having lost all force, unless they are found in the approved liturgical books, or they are laws derived from the natural and the positive divine law.

“The Church therefore is a society that is essentially monarchical. But this does not prevent the Church, for a short time after the death of a pope, or even for many years, from remaining deprived of her head. [vel etiam per plures annos capite suo destituta manet]. Her monarchical form also remains intact in this state . . .
“Thus the Church is then indeed a headless body . . . Her monarchical form of government remains, though then in a different way —that is, it remains incomplete and to be completed. The ordering of the whole to submission to her Primate is present, even though actual submission is not . . .
“For this reason, the See of Rome is rightly said to remain after the person sitting in it has died —for the See of Rome consists essentially in the rights of the Primate.
“These rights are an essential and necessary element of the Church. With them, moreover, the Primacy then continues, at least morally. The perennial physical presence of the person of the head, however,[perennitas autem physica personis principis] is not so strictly necessary” (De Ecclesia 2:196-7).

“We may here stop to inquire what is to be said of the position, at that time, of the three claimants, and their rights with regard to the Papacy. In the first place, there was all throughout, from the death of Gregory XI in 1378, a Pope —with the exception, of course, of the intervals between deaths and elections to fill up the vacancies thereby created. There was, I say, at every given time a Pope, really invested with the dignity of vicar of Christ and Head of the Church, whatever opinions might exist among many as to his genuineness; not that an interregnum covering the whole period would have been impossible or inconsistent with the promises of Christ, for this is by no means manifest, but that, as a matter of fact, there was not such an interregnum.”

B. The Church During a Vacancy of the Holy See
We must not think of the church, when the Pope is dead, as possessing the papal power in act, in a state of diffusion, so that she herself can delegate it to the next Pope in whom it will be recondensed and made definite. When the Pope dies the Church is widowed, and, in respect of the visible universal jurisdiction, she is truly acephalous.* ‘But she is not acephalous as are the schismatic Churches, nor like a body on the way to decomposition. Christ directs her from heaven .. . But, though slowed down, the pulse of life has not left the Church; she possesses the power of the Papacy in potency, in the sense that Christ, who has willed her always to depend on a visible pastor, has given her power to designate the man to who He will Himself commit the keys of the Kingdom of Heaven, as once He committed them to Peter.
*During a vacancy of the Apostolic See, says Cajetan, the universal Church is in an imperfect state; she is like an amputated body, not an integral body. “The Church is acephalous, deprived of her highest part and power.”

“During a vacancy of the Apostolic See, neither the Church nor the Council can contravene the provisions already laid down to determine the valid mode of election (Cardinal Cajetan, O.P., in De Comparata, cap. xiii, no. 202). However, in case of permission (for example if the Pope has provided nothing against it), or in case of ambiguity (for example, if it is unknown who the true Cardinals are or who the true Pope is, as was the case at the time of the Great Schism), the power ‘of applying the Papacy to such and such a person’ devolves on the universal Church, the Church of God.”

“. . . by exception and by suppletory manner this power (that of electing a pope), corresponds to the Church and to the Council, either by the inexistence of Cardinal Electors, or because they are doubtful, or the election itself is uncertain, as it happens at the time of a schism.”

“When it would be necessary to proceed with the election, if it is impossible to follow the regulations of papal law, as was the case during the Great Western Schism, one can accept, without difficulty, that the power of election could be transferred to a General Council.”
“Because ‘natural law prescribes that, in such cases, the power of a Superior is passed to the immediate inferior, because this is absolutely necessary for the survival of the society and to avoid the tribulations of extreme need.”

“Even if St. Peter would have not determined anything, once he was dead, the Church had the power to substitute him and appoint a successor to him… If by any calamity, war or plague, all Cardinals would be lacking, we cannot doubt that the Church could provide for herself a Holy Father.
“Hence such an election; ‘a tota Ecclesia debet provideri et non ab aliqua partuculari Ecclesia.’ (“It should be carried by all the Church and not by any particular Church.”) And this is because “Ilia potestas est communis et spectat ad totam Ecclesiam. Ergo a tata Ecclesia debet provideri.’” (“That power is common and it concerns the whole Church. So it must be the duty of the whole Church.”)

“Immediately, one ought to resists in facie, a pope who is publicly destroying the Church; for example, to want to give ecclesiastical benefits for money or charge of services. And one ought to refuse, with all obedience and respect, and not to give possession of these benefits to those who bought them.”

“What is there to do when the pope wishes without reason to abrogate the positive right order? To this he responds, ‘He certainly sins; one ought not to permit him to proceed thus, nor ought one to obey him in what is bad; one ought to resist him with a polite reprehension. In consequence, if he wished to deliver all the treasures of the Church and the patrimony of St. Peter to his parents; if he was left to destroy the Church or in similar works, one ought not to permit him to work in this form, having the obligation of giving him resistance. And the reason for this is, in these matters he has no right to destroy. Immediately evident of what he is doing, it is licit to resist him. Of all this it results that, if the pope, by his order or his acts, destroys the Church, one can resist and impede the execution of his commands.’”

“If the pope gave an order contrary to the good customs, one should not obey him; if his intent is to do something manifestly opposed to justice and the common good, it is lawful and valid to resist; if attacked by force, one shall be able to resist with force, with the moderation appropriate to a just defense.”

“Just as it is licit to resist a Pontiff that attacks the body, it is also licit to resist (him) who attacks the soul, or who disturbs the civil order, or, above all, he who intends to destroy the Church. I say it is licit to resist by not doing what he orders and by impeding the execution of that which he wills. It is not licit, with everything, to judge him impose a punishment, or depose him, for these actions are accorded to one superior to the pope.”

“Now when the Pope is explicitly a heretic, he falls ipso facto from his dignity and out of the Church . . . ”

“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.”

“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.”

“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.”

“Through notorious and openly divulged heresy, the Roman Pontiff, should he fall into heresy, by that very fact(ipso facto) is deemed to be deprived of the power of jurisdiction even before any declaratory judgment by the Church… A Pope who falls into public heresy would cease ipso facto to be a member of the Church; therefore, he would also cease to be head of the Church.” And also: “A doubtful pope is no pope.”

“The Pope himself, if notoriously guilty of heresy, would cease to be Pope because he would cease to be a member of the Church.”

“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.’”

“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.”

“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.”

“‘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.”

While the popes since vatican II have been heretical  and the council itself as well,what substantiates this position?
Sources?
Thanks

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This whole post was excellent so I don't want to sound like I'm arguing, but I don't think these two are possibilities. They effectively change the protection of the pope from "The pope cannot do X, Y or Z" to "The pope cannot to X, Y or Z unless he is being blackmailed or drugged." I believe the first of those statements is the correct one.

If a pope could promulgate false liturgies, etc. when he is drugged or blackmailed, this renders any papal protection void, since it is impossible to know if a pope is being blackmailed or drugged, and anyone could reject what a pope promulgates by saying he was probably blackmailed or drugged.