Fr. Peter Scott (SSPX) explains:
"Are the Church’s disciplinary laws infallible?
This theological question is an important one, and has not yet been adequately treated. Fr. Laisney spoke of it in the March 1997 issue of The Angelus (pp. 31-40) regarding the question of the New Mass, and the opinion (a priori) of those who say that it is infallible since it was "promulgated" by the pope, and that consequently it can contain no error or evil. This is manifestly false, just like the new Code of Canon Law (1983) and the new Catechism of the Catholic Church.
This is the principle which both sedevacantists and conservatives use against the position of accepting everything Catholic which the pope legislates and refusing that which is not entirely Catholic. This position is but common sense.
It is certainly true that, before Vatican II, pious theologians proposed that the pope’s infallibility should extend to his legislative acts. We know, however, that if such a thesis be accepted, that it does not and cannot include all his legislative acts, any more than his infallibility can include all his teaching acts.
It is only indirectly that legislative acts teach dogma. It is certainly reasonable that a legislative act of the pope would in this way participate in the infallibility of the Ordinary Magisterium of the Church. It could not, however, participate in the infallibility of the Extraordinary Magisterium, for there is not in a legislative act a formal definition of a dogma. It can, therefore, only participate in the infallibility of the Ordinary Magisterium.
The conditions for the infallibility of the Ordinary Magisterium are that that which is taught, has been taught ubique, semper et ab omnibus; that is, always, everywhere and by all. I refer you to the essays on the infallibility of the Ordinary Magisterium in Angelus Press’s book,
Pope or Church? It could easily be considered that the promulgation of Quo Primum does just that, inasmuch as it is a formal codification of a rite of Mass which perfectly expresses the Catholic doctrine taught by the Council of Trent. However, there is no way that new or revolutionary legislation could participate in this infallibility, any more than could the dogmatic decrees of Vatican II participate in this infallibility, for they are not even a part of the Ordinary Magisterium of the Church when they teach novelties.
Consequently, it comes down to examining the laws (such as the new Catechism of the Catholic Church) and seeing what is perfectly in conformity to what has always and everywhere been taught by all Catholics. Such laws express the infallibility of the Church, inasmuch as they express Catholic doctrine, even though they do not make a direct definition. Other laws either do not express Catholic doctrine, or express something contrary to it (e.g., ecuмenism), which means that for serious reasons of Faith we may and should question and refuse them.
[Answered by Fr. Peter R. Scott]"
Brief Commentary:
It is precisely because the teachings of the magisterium must be universal in space (i.e., geographical), (morally) unanimously, and time, that sedevacantists reject this latter criteria of temporal universality, in order to make EVERYTHING part of the ordinary magisterium, and thereby conclude the conciliar and post-conciliar popes, having taught heresy, cannot have been popes). In rejecting temporal universality, they reject the teaching of St. Vincent of Lerrins (Commonitorium), so esteemed in the Church, and arrive at their error.