Here is an exact copy of what I posted...
I would like to point out something important about this.
This work of St. Francis de Sales is definitive on this matter. Seven years after the dogma of "papal infallibility" was defined in 1870 (at the General Council), in 1877 the same pope, Pius IX, raised this Saint to a "Doctor of the Church". On that occasion the pope called this work, "a complete demonstration of the Catholic religion". After all, when the Saint wrote it, he was writing it to Protestants about the Catholic Church.
Another interesting thing is that the General Council of the Vatican in 1870 took care to condemn what we now refer to as "Gallicanism" or "Conciliarism". Basically saying that nobody can judge a pope. In light of this, we know that this quote promotes no such error. Here is the excerpt:
"when he is explicitly a heretic, he falls ipso facto from his dignity and out of the Church, and the Church must either deprive him or, as some say, declare him deprived, of his Apostolic See, and must say as St. Peter did: let another take his bishopric"
This means that the prelates of the Church who gather to take care of the matter, would be gathering having already personally (even lying in bed one night) concluded that the man is no longer the pope, otherwise the gathering against a believed-to-be-pope would be heretical and a mortal sin.
And so it is across the board with Catholic publications since then. An example is "A Catholic Dictionary", going through several editions in the 1900's saying:
"A pope can only be deposed for heresy, expressed or implied, and then only by a general council. It is not strictly deposition, but a declaration of fact, since by his heresy he has already ceased to be head of the Church... "
- A Catholic Dictionary, 1951. Pope, Deposition of a
"An heretical pope necessarily ceases to be head of the Church, for by his heresy he is no longer a member thereof: in the event of his still claiming the Roman see a general council, improperly so-called because without the pope, could remove him. But this is not deposition, since by his own act he is no longer pope."
- A Catholic Dictionary, 1951. Deposition