I recall the Vatican responding to Cardinal Sara when he tried to make it the norm that the celebrant
say Mass Ad Orientem. He was informed that his words were not in line with Vatican II. There
was another issue, but I forget what it was.
Vatican II officially encouraged the celebration of Mass "facing the people" (versus populum), but the historic practice of "facing East" (ad orientem) is still permitted in the reformed Mass and normative for the traditional Latin Mass.
However, this option can only occur in the Novus Ordo a Mass "facing the people" is not an option for the TLM.
What the Church permits, can be done, what it prohibits, cannot be done.
It was the authority of the diocesan Bishops. As the
CONSTITUTION
ON THE SACRED LITURGY
SACROSANCTUM CONCILIUM
States;
"1) The competent territorial ecclesiastical authority mentioned in Art. 22, 2, must, in this matter, carefully and prudently consider which elements from the traditions and culture of individual peoples might appropriately be admitted into divine worship. Adaptations which are judged to be useful or necessary should then be submitted to the Apostolic See, by whose consent they may be introduced.
2) To ensure that adaptations may be made with all the circumspection which they demand, the Apostolic See will grant power to this same territorial ecclesiastical authority to permit and to direct, as the case requires, the necessary preliminary experiments over a determined period of time among certain groups suited for the purpose.
3) Because liturgical laws often involve special difficulties with respect to adaptation, particularly in mission lands, men who are experts in these matters must be employed to formulate them.
Sacrosanctum Concilium "
After experimentation decades ago, the USCCB have made the norm for the celebrant to face the people in
the Novus Ordo format.
Mother Angelica got into an argument with Bishop Foley over this, in fact he left EWTN over it.
The ruling from the Vatican was that because it was a religious order, the celebrant could
celebrate at the shrine church, according to the norms of the order, Ad Orientem.
However, the Mass which is televised from the chapel and presented to the public,
the celebrant must face the people according to the norm by the USCCB.