Samuel quotes Archbishop Lefebvre as saying:
"Thirdly, we pointed out that, despite the testimony of Tradition which has been alleged, there are also serious reasons, both doctrinal and historical for us, to doubt that universal laws always and necessarily imply the infallibility of the Church."
If the Archbishop is correct, then it is not necessarily the case that, "if the pope is not doubtful, then the rite is not doubtful" (as 2Vermont and Ladislaus are contending).