Matto - I think you watched the same fr. chazal nfp conference that I did. And, from what I understand, humanae vitae was the last stop in terms of nfp. When looked at, the church has gone through stages with this. First, it was a subject that required clerical permission you could say(left to the confessional to deal with onanism). Then, Pius XII informed the public that there were four conditions allowing its use(this in essence removes clerical permission). Then, Paul VI in humanae vitae(from what I recall) gave approval and did away with if not officially reversed the ordered ends of marriage.(no restriction/no sin). The sin that once was(read casti conubii - refers to reversing the ordered ends of marriage as a "grave sin" - Fr. Jenkins on wcb inferred that it was dogmatic) is now no longer with humanae vitae. And, Fr. Chazal may have considered it the last acceptable encyclical for a while, but that does not mean the sspx officially and as a whole did.