cites pre-Vatican II theological sources
The link looks to be spot on and agrees with what I said - that the magisterium is always infallible. Thanks for the link!
In conclusion we shall excerpt the text of a theologian, whose passing is much to be regretted, who had a very clear grasp of the doctrine we are recalling here, and who knew well that it had been brought into confusion by the New Theologians.
In arguing against Joseph KIeiner on the manifest contradiction between Pope Pius VI's Auctorem Fidei, which condemns concelebration, and Pope Paul VI's Instructio, which encourages it, Fr. Joseph de SainteMarie, O.C.D., wrote:
Has it ever been known for the Magisterium to intervene against a declaration of the Magisterium? In his mind [i.e., ofJoseph Kleiner - Ed.] the reply must be in the negative: No, for the sake of the infallibility of the Magisterium. This infallibility does imply, of course, that the Church cannot contradict herself, but only under a condition which our author has forgotten, namely, that she engages the fullness of her infallibility in such an act; or, in the case of the Ordinary Magisterium (and we must take great care not to minimize the latter's authority), provided that it conforms to what the Infallible Magisterium teaches, either in its solemn acts or in its constant teaching.
If these conditions are not respected, there is nothing impossible about one "intervention" of the Magisterium being in contradiction with another. There is nothing to trouble one's faith here, for infallibility is not involved; but people's Catholic sensibilities are right to be scandalized at it, for such facts reveal a profound disorder in the exercise of the Magisterium. To deny the existence of these facts in the name of an erroneous understanding of the Church's infallibility, and to deny it a priori, is to fly in the face of the demands of theology, of history, and of the most elementary common sense.