The Church is indefectible, therefore, any Pope accepted by the body of Bishops is de facto a valid Pope, even if his election were invalid. For the body cannot go astray following a false head.
However, the fathers and doctors of the Church all agree that IF a Pope ever were a manifest heretic, he would cease to be a valid Pope, for one cannot be the head of a Church of which one is not a member, and heretics are automatically excommunicated.
So how is it that most papal accusers claim Francis is valid, and that he has committed heresy? Both those claims cannot be true.
Why won’t the papal accusers answer this simple question: If Francis is guilty of heresy, apostasy, and idolatry, as you claim, how can he be the valid Pope? They won’t answer because they don’t want people to know that they are schismatics who reject the Pope.
Bellarmine: “a Pope who is a manifest heretic, ceases in himself to be Pope and head, just as he ceases in himself to be a Christian and member of the body of the Church: whereby, he can be judged and punished by the Church. This is the opinion of all the ancient Fathers, who teach that manifest heretics soon lose all jurisdiction….”
And that includes Bishops as well. Any Bishop who is a manifest heretic “ceases in himself to be a Christian and member of the body of the Church”. Bishop Carlo Vigano and Bishop Athanasius Schneider are both manifest heretics, they both have lost all jurisdiction, they both have ceased to be Christians, in the fullest sense, and ceased to be full members of the body of the Church. There is some sense in which heretics and schismatics might be members implicitly, or in the sense of having the indelible characters of the three Sacraments. But they no longer have the authority of Bishops.
Therefore, Vigano and Schneider cannot propose to correct the Roman Pontiffs based on their role as Bishops. They have lost that role, that authority, and so they cannot appeal to what they have lost as a way to rebuke a Pope or a Council.