A liturgical form can have full canonical status; and when it does, it is clear that a cleric is (for example) fulfilling his obligation to the Office by using it. But the Latin term auctoritas has a more subtle sense than mere canonical liceity. It might suggest the personal influence which a player in Roman politics had, quite distinct from any imperium which he might enjoy as a result of a magistracy which he held. Or a sense of authoritativeness or impressiveness, of personal prestige or repute; we all know the sort of person who, perhaps in a committee or gathering, is listened to the moment he opens his mouth and whose interventions invite a respect out of all proportion to his merely legal status. It is a characteristic of the Good Woman in Proverbs that her husband is great among the elders at the gate; when such people are moved to utterance, other people put their hands to their mouths. In our secular politics, the policies which were embodied in the manifesto of a government which has won power by a sweeping majority have auctoritas greater than the ideas dreamed up last night by a premier who is holding onto power by his fingertips ... although the constitutional power may be formally the same in each case.
Auctoritas as opposed to mere canonical liceity has always had a place in Liturgy. When manualists such as the admirable O'Connell talked about a custom which is even contra legem enjoying by virtue of its longevity not merely liceity but even prescription above the letter of the rubric, it is in a way auctoritas that they are talking about. But I contend that the radical changes that followed Vatican II raise the question of auctoritas in new, difficult, and acute forms. The basic reason for this is the most striking novelty involved in post-Conciliar liturgical texts: multiple choices facing a celebrant or a worshipping community as they prepare to celebrate a rite. What every celebrant said daily at every altar of the Roman Rite throughout the world for centuries obviously had enormous auctoritas. A novel formula which has just been put on some menu from which choices are to be made, manifestly has very much less. Whereas, before the Council, something that auctoritas urged one to do was broadly in line with what was canonically licit, after the Conciliar 'reforms' auctoritas and liceity might find themselves standing further and further apart from each other.
I strongly agree with Joseph Ratzinger's view that there is something highly questionable about the idea that a Roman Pontiff can do anything especially if backed by a mandate of an ecumenical council. Still less would I agree that legislative bodies inferior to the Pontiff himself have such power. I would contend that what is wrong with that idea is, among other things, its forgetfulness of liturgical auctoritas. And my inclination is to believe that, in many and important respects, the 'reforms' went beyond the conciliar mandate of Sacrosanctum Concilium (praeter concilium) and, even more problematically, in some cases directly contradicted it (contra concilium). In my view, changes praeter Concilium have less auctoritas than those which do rest on a conciliar mandate; and changes contra Concilium raise, as Benedict XVI implied, extremely acute difficulties with regard to their auctoritas.
I expect some Catholic readers may feel uneasy about the path I am treading. This is because the Catholic Church, more than most ecclesial bodies, has a deeply ingrained sense of Law. This makes it easy for Roman Catholics to underestimate the force of auctoritas. But Benedict XVI was appealing directly to this when he wrote "What earlier generations held as sacred, remains sacred and great for us too, and it cannot be all of a sudden entirely forbidden or even considered harmful". In so teaching, in so using the word "cannot", he was not speaking in terms of canonical or legislative details; he was arguing theologically.
Cardinal Nichols, or his advisers, were quite mistaken in their arguments, drawn from misunderstood details in the Latin of legislative texts, in claiming the illegality of celebrating the Novus Ordo versus apsidem (incidentally, if this were so, why have successive Archbishops of Westminster since Vatican II never brought the Brompton Oratory to heel?).
But, even had they been right, this would not have dimished the overwhelming force, based on well-nigh universal custom and Patristic testimony, of the auctoritas of versus Orientem and versus apsidem.