[ninenot]

In this particular case you are wrong in the premise.

The regulation of liturgy is reserved to the Pope because the liturgy is doctrinal by its very nature. That is, the pope cannot allow a "heretical" liturgy.

Thus, this is NOT an error--it involves infallibility--(faith)--and after the review of the Pope (and others, you can be sure) it's a done deal.

[narses]

So you're suggesting that if HH said "there is no Real Presence but the Mass is still valid", you'd accept that?

[narses]

Hence doctrinal decisions or instructions issued by the Roman congregations, even when approved by the pope in the ordinary way, have no claim to be considered infallible.

From http://www.newadvent.org/cathen/07790a.htm#IIIB