[Unam Sanctam]

The SSPX has refused obedience to legitimate authority as regards lawful commands and without necessity. The specific form of the liturgy is something within the power of the Pope to regulate, so long as the essence of the Eucharistic sacrifice is maintained, and therefore there is no necessity to disobey, and certainly not now that indult Tridentine masses are allowed.

[AskStPhilomena]

"The specific form of the liturgy is something within the power of the Pope to regulate, so long as the essence of the Eucharistic sacrifice is maintained"

Here's a book by an eminent doctor of sacred theology (Rev Fr. Trinchard) that may interest you...
http://www.maeta.com/
Whether invalid or not, the short answer to the novus ordo is NO!

[ultima ratio]

The refusal was not only canonically permitted, it was necessary. The Church was and remains in crisis. It doesn't matter if the Pope believes it is so or not. He has been wrong about a lot of things.

[Mark in the Old South]

Re: "The SSPX has refused obedience to legitimate authority as regards lawful commands and without necessity" Let me repeat "WITHOUT NECESSITY"

That is really the sticking point is it not? You think it is without necessity and we do. It is a wonder to me but clearly you think the problems of the Church are minor or at least do not rise to the level our Blessed Archbishop did. I'll stand with the Archbishop. I have been reading the book Vows of Silence, it is so depressing. Many Protestants have no clue how bad the rot is in the Church and many more Catholics refuse it see it. It is so depressing. It has cleared on thing up for me. When reading the Gospels I could not quite understand why Christ was so hard on the Jewish leaders of His day. Consider how bad the Hebrews had been in the past, idol worship, temple prostitutes, child sacrifice to strange gods, none of that was happening at the time of Christ except by the Romans so why the hard words. I can see now how an institution can become so corrupted, so valueless that they loose sight of their higher calling. Unfortunately pride, avarice and lust seems to be more attractive to some.

So in conclusion,I very much doubt there will ever be a point where fans of Vatican II will smell that pot of coffee. And those priest in SSPX who are unhappy? You can have them if you want. One word of caution you get them "as is", if you think the SSPX is being unfair and too hard on them just remember Urriogotty, you rescued him from those mean old SSPX Bishops as well.