The SSPX witness regarding Archbishop Lefevbre and the New Mass, which was promulgated after Vatican II in 1970:
"In the following statement dated 8 November 1979, Archbishop Lefebvre clarified his position and that of the Society of St. Pius X on the subject of the New Mass and the Pope. This clarification had been made necessary by the growing number of traditional Catholics who claimed that the New Mass was intrinsically invalid, even in its papally approved Latin version, and that the Holy See was vacant. In the latter case, some claimed that Pope Paul VI had been a heretic before assuming office, and had never been truly Pope, and others alleged that he had lost his office through heresy. These two opinions certainly have an emotional rather than a theological basis...In the case of the New Mass, it is evident that while still upholding its intrinsic validity, the Archbishop has adopted a more negative stance towards assisting at it than he did in earlier years.
"This is not surprising, because, as the years have passed, the manner in which the New Mass is (1) celebrated has become consistently more unacceptable in many parishes. Matters had reached the stage in 1980 that Pope John Paul II needed to offer an apology to the faithful for the scandal and disturbance caused to them by the way the New Mass was so frequently celebrated.
"Unfortunately, the Archbishop's statement was not as clearly worded as it might have been on the matter. One passage in particular gave some readers the impression that the Archbishop had stated that a Catholic could never fulfil his Sunday obligation by assisting at the New Mass. Among those who had received this impression from the statement was Cardinal Seper, who mentioned the anxiety it had caused him during an interview he granted me at Easter 1980. I had the opportunity of a long interview with the Archbishop a few weeks later when we discussed the matter. He was kind enough to summarize his considered opinion for me in writing (dated 9 May 1980). It read as follows:
Those who feel themselves obliged in conscience to assist at the New Mass on Sunday can fulfil their Sunday obligation. But one cannot accuse a person of a grave fault because he prefers not to assist at Mass on Sunday rather than assist at the New Mass.
Thus where the Archbishop states that “these New Masses are incapable of fulfilling our Sunday obligation,” he is referring to New Masses which involve “sacrilegious acts which pervert the faith by diminishing it.” The declaration which he made at my request makes it quite clear that this was indeed his meaning.---Apologia pro Marcel Lefebvre by Michael Davies, Volume 2, Chapter XL
"The Holy Council [of Trent] declares moreover: The Church has always had, in the dispensation of the sacraments, their substance being saved, the power to decide or to modify what she judges better to suit the spiritual utility of those who receive them or with respect to the sacraments themselves, according to the variety of circumstances, times and places. The Council of Trent, Dz 1728; also Dz Herder ed, 1955, #931, p. 256 " (/blockquote>
(1) Note this was written of course before the reform of the reform which began with JPII & was continued decisively under Benedict XVI.
--->On the Validity of the 1970 (Novus Ordo) Missal of Paul VI ---by Michael Davies...