A true pope cannot fall under the jurisdiction of the Church (or even a future or past pope as an equal cannot judge an equal). Only a dubious pope can fall under its jurisdiction.
“Suarez explained: ‘… nor can the Pontiff ipso facto forfeit his dignity by means of any human law, since it would be issued by an inferior, such as a Council, or by an equal, that is, a predecessor Pope; and none of these has coercive force, to be able to punish a Pope who is equal, or a superior.’ The loss of office does not arise from any human law, but from the nature of heresy; as Bellarmine explains in De Romano Pontifice II, xxx, quoting the unanimous teaching of the Fathers: ‘Nam Patres illi dicunt hæreticos amittere jurisdictionem, non allegant ulla jura humana, quæ etiam forte tunc nulla extabant de hac re: sed argumentantur ex natura hæresis’.”
“Peter was given the full power of primacy, and the apostles were given the power to exercise jurisdiction in hierarchical subordination to that primacy; consequently, the whole assembled Church, whose jurisdiction, by its very nature, exists in hierarchical subordination to the primacy of the Pope’s jurisdiction, has absolutely no power to judge or depose a validly reigning pontiff.
“The fact that the members should prevail over the head or cut off the head is against nature: ‘Moreover, the fact that the head is governed by the members, and not rather that the members are governed by the head, is against nature, just as it is against nature for the members to cut off the head, when by chance he is seriously ill.’ For these reasons, Bellarmine explains that it is only when the Pope is dubious or not a Pope, that a council can judge who the Pope is or provide a true pastor for the Church. And further down the page he clarifies: ‘Because a doubtful Pope is not considered a Pope, and therefore having power over him does not mean having power over the Pope.’ For this reason, Bellarmine explains in CAPUT ix. (De utilitate vel etiam necessitate celebrandorum comciliorum) of De Concilliis et Ecclesia, that one of the reasons that would make it necessary to convoke a council would be ‘the suspicion of heresy in the Roman Pontiff, if it were to happen.’ Bordoni also explains that only a true and certain Pope is above a council, but doubtful Popes and pertinacious heretics (because they are incapable subjects) are subject to a council: solus verus et indubitatus Papa est supra Concilium, et non alii de quibus dubitatur, ergo subijciuntur Concilio. In such situations as these, according to the most eminent authorities, the Apostolic See is considered vacant, and it is precisely when in such a case that the Pope is found to be an obstinate heretic, the judgment [in the words of Pope Gregory XVI] would not be made against the actually reigning Pope, ‘but only against the person who was formerly adorned with the papal dignity.’ Then, for this reason that the see would be presumed vacant, Bellarmine says: ‘In this case a council may examine the case of the pontiff, and if it should find that the pope is really an infidel, it may declare him out of the Church and condemn him.'”
The following is the original written by St. Robert Bellarmine regarding one of the causes that permits the Church to convoke a council against a dubious pope, that is, for suspicion of heresy against him:
