https://cmri.org/articles-on-the-traditional-catholic-faith/quotes-from-theologians-supporting-the-sedevacantist-position/
“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.
Right, let us put this to the test, a real problem for sedevacantism:
THE COUNCIL OF TRENT (1545-1563):‘The sacred and holy, ecuмenical, and general Synod of Trent, - lawfully assembled in the Holy Ghost, the Same three legates of the Apostolic See presiding therein, -
‘Furthermore, in order to curb imprudent clever persons, the synod decrees that no one who relies on his own judgment in matters of faith and morals, which pertain to the building up of Christian doctrine, and that no one who distorts the Sacred Scripture according to his own opinions, shall dare to interpret the said Sacred Scripture contrary to that sense which is held by holy Mother Church, whose duty it is to judge regarding the true sense and interpretation of the Holy Scriptures,
or even contrary to the unanimous consent of the Fathers, even though interpretations of this kind were never intended to be brought to light. Let those who shall oppose this be reported by their ordinaries and be punished with the penalties prescribed by law.’ -- (Denzinger – 783/786)
On February 24th 1616 the assessments of Galileo's heliocentrism were declared:
(1) “That the sun is in the centre of the world and altogether immovable by local movement,” was unanimously declared to be “foolish, philosophically absurd,
and formally heretical [denial of a revelation by God] inasmuch as it expressly contradicts the declarations of Holy Scripture in many passages, according to the proper meaning of the language used,
and the sense in which they have been expounded and understood by the Fathers and theologians.”(
considered an immutable, irreformable truth in virtue of the fact that this revelation had been constantly preserved and held by Church tradition since the time of the Apostles);
(2) “That the Earth is not the centre of the world, and moves as a whole, and also with a diurnal movement,” was unanimously declared “to deserve the same censure philosophically, and, theologically considered to be at least erroneous in faith.”
THEN IN 1820 Pope Pius VII decrees:
1820 Decree states: ‘The Assessor of the Holy Office has referred the request of Giuseppe Settele, Professor of Astronomy at La Sapienza University, regarding permission to publish his work Elements of Astronomy in which he espouses the common opinion of the astronomers of our time regarding
the Earth’s daily and yearly motions, to His Holiness through Divine Providence, Pope Pius VII…
.His Holiness has decreed that no obstacles exist for those who sustain Copernicus’ affirmation regarding the Earth’s movement in the manner in which it is affirmed today, even by Catholic authors. THEN IN 1882 Pope Pius VII decrees again:
‘The most excellent [Holy Office] have decreed that there must be
no denial, by the present or by future Masters of the Sacred Apostolic Palace, of permission to print and
to publish works which treat of the mobility of the Earth and of the immobility of the sun [the defined heresy in 1616], according to the common opinion of modern astronomers, as long as there are no other contrary indications, on the basis of the decrees of the Sacred Congregation of the Index of 1757 and of this Supreme [Holy Office] of 1820; and that those who would show themselves to be reluctant or would disobey, should be forced under punishments at the choice of [this] Sacred Congregation, with derogation of [their] claimed privileges, where necessary.’
Inherent in the above two decrees of 1820 and 1822 is that you the flock can ignore the defined and declared heresy regarding the interpretation of Divine Scripture as held by all the Fathers.
It seems then, since 1820 we have had popes not only tolerating but believing and teaching what the Church defined as FORMAL heresy, in other words a heresy that had been long condemned as heresy in the past was made FORMAL HERESY in 1616 and confirmed again as formal heresy by Pope Urban VIII in 1633.