CathInfo.com

You never cease to amaze, now going so far as to distort / warp cuм ex into an endorsement of R&R.  Entire point of the docuмent is that a Pope who has deviated from the faith ceases to be pope.  This reference to judging has to do with the individual, having fallen from the papacy, and not with the Pope as pope.  It's along the lines of what Pope Innocent III wrote before him:

As Fr. Kramer points out, since Vatican I, the theological maxim papa a nemine judicandus has been elevated to near dogmatic status, and is the entire rationale for the papa haereticus ipso facto depositus position, namely, that the only way a Pope can be judged as guilty of heresy is if he's already ceased to be Pope first.

Does any docuмent actually say that a pope ceases to be pope due to heresy? 

Are you deranged?  You seem to have a seriously unhealthy obsession with Bishop Pivarunas and Archbishop Thuc.  At no time in the entire lengthy article about the inconsistent theological position of +Lefebvre did he even mention Archbishop Thuc.  You also just outright lie about +Thuc ... apparently having no issues with calumny.  +Thuc was no "liberal at V2" but was part of the same group of conservative Fathers as +Lefebvre.  +Lefebvre asked +Thuc to start and run the seminary at Econe original, but +Thuc declined, feeling that he did not have the energy left at his age to undertake it.  +Thuc held two advanced degrees from Rome and had in fact founded and set up seminaries from scratch (the reason +Lefebvre initially asked him).  +Thuc was more of a trained theologian than +Lefebvre ever was.  Nor is Bishop Pivarunas alone in pointing out the inconsistencies in the position of the SSPX, as many extremely well-trained clergy (whatever you want to falsely smear +Pivarunas with) are in complete agreement with the criticisms he's making here ... not the least of whom was Bishop Guerard des Lauriers, who was arguably the top theologian in the Church before V2.

Many extremely well trained clergy? Pivarunas was trained by a quack (Shuckhardt, who had some guy make him a so called bishop). So you can't use the the "extremely well trained" on the c m r i clergy trained under Piv as your best defense for Piv's stupid theory that Archbishop Lefebvre was inconsistent. The more I look into the c m r i the more I am astonished how people find this group credible. The only reason I had to learn about them was because of acquaintances who latched onto them.
Piv has to criticize Archbishop Lefebvre and praise the V2 liberal Thuc because that is all he has to make himself and the c m r i look credible.
And des Lauriers probably had no practical experience in the missionary field where Archbishop Lefebvre had immense experience, enough experience to know that this stupid sedeprivationist theory would only confuse and derange catholics who do not have an ounce of theological training. Archbishop Lefebvre knew it was dangerous and that's why he expelled des Lauriers.
These sedes are influencing normal catholics (good people) to make a judgement they have no authority to make, once they make that judgement they will assume they have that ability to judge others and defined truths and morals. It opens up a pandora's box in their head. They plant a seed of self authority that will eventually be defended by pride.