I’ve been asked by several people whether or not a diocesan bishop has authority on his own to require only versus populum celebration of Mass in the Novus Ordo.
This seems to be what the Archbishop of Detroit desires. I’ve posted on this elsewhere and Rorate has the screenshot. Here it is again:

He says under point H:
“use of the ad orientem posture by the priest when using the ordinary form of the Mass is no longer permitted”.
However, in point I he says:
“no cleric… may add omit, or alter anything in the ordinary form of the Mass”.
PROBLEM: The ad orientem posture IS THE NORMAL posture of the “ordinary form” (i.e. Novus Ordo).
I’m not the Dicastery for Divine Worship so I cannot definitely close the issue.
I can add this for consideration.
The current Novus Ordo Missale Romanum presumes that there are times when the celebrant (and the deacon) must turn to face the people and then turn back to the altar.
Bishops have tried these shenanigans before and the (then) Congregation for Divine Worship had to break it down barney style for them because, as it seems, the bishops didn’t know Latin (or they ignored the Latin).
In 2000, the CDW’s Prefect Jorge A. Cardinal Medina Estévez explained in a letter (10 April 2000 PROTOCOL NO. 564/00/L) to the Bishop of Boise what the situation is with ad orientem worship. Cutting to the chase:
This dicastery wishes to state that Holy Mass may be celebrated versus populum or versus apsidem. Both positions are in accord with liturgical law; both are to be considered correct. There is no preference expressed in the liturgical legislation for either position. As both positions enjoy the favor of law, the legislation may not be invoked to say that one position or the other accords more closely with the mind of the Church.
What do the rubrics of the Novus Ordo say?
In the Novus Ordo Missale Romanum we find, for example, before the Ecce Agnus Dei. Remember that LATIN and not English is the official language (my emphasis):
132. Sacerdos genuflectit, accipit hostiam, eamque aliquantulum elevatam super patenam vel super calicem tenens, versus ad populum, clara voce dicit:
That versus is from the verb verto, “to turn, to turn round or about“. That’s why the Latin substantive versus -us means a “furrow” because when plowing you turn around at the end and go back and forth.
The Latin rubric means:
The priest genuflects, takes the host and, holding it elevated a little over the paten or the chalice, having turned around toward the people says in a clear voce:
Pretty clear. That’s the rubric in the Church’s normative Missale for the Novus Ordo.
Hence, not to turn around is to omit or alter something. On the one hand, the Archbishop is saying “you can’t make changes, additions or omissions” even as he is saying “you must not follow the rubrics”.
In case you were wondering, the next rubric gets the priest turned back to the altar again:
133. Et sacerdos, versus ad altare, secreto dicit:
And the priest, having turned around toward the altar, says quietly:
There is another rubric, 127 at the sign of peace, which uses the participle conversus from converto (“to turn, wheel about”).
Of course now we have to get into the question of the position of the altar.
If the altar is detached from the wall so that it can be used from either side, then that rubric isn’t going to be literally applied because the priest is already versus ad populum. We wind up with this same issue in the Vetus Ordo in Rome in basilicas which have an entrance to a crypt directly in front of and under the main altar, as in Santa Cecilia or San Nicola in Carcere.
The problem is that clerics who don’t read Latin are basing their notions on the positions of altars and celebrations ad populum versus on a faulty English translation of GIRM 299.
I wrote about this nasty business for YEARS and now it is BACK because people DON’T READ LATIN. If they know a smidge of Latin, they often unwarily or ignorantly try to render Latin texts into English according to the Latin word order. But that’s not how Latin works! English works that way, mostly, but not Latin.
Here is, again, GIRM 299:
299. Altare maius exstruatur a pariete seiunctum, ut facile circumiri et in eo celebratio versus populum peragi possit, quod expedit ubicumque possibile sit.
For years now, the ignorant (or purposely shifty) have relied on this BAD translation… I repeat, BAD as in inaccurate to the point of being deceptive:
299. The altar should be built separate from the wall, in such a way that it is possible to walk around it easily and that Mass can be celebrated at it facing the people, which is desirable wherever possible.
The problem with the translation is that it gives the impression that it is celebration versus populum which is desirable, rather than the separation of the altar from the wall.
I corrected this BAD translation many times here and in print in The Wanderer.
The late fabled Latinist Fr. Reginald Foster corrected it.
THE PREFECT of the CDW, Card. Medina Estévez corrected it.
Now a good translation.
299. The main altar should be built separated from the wall, which is useful wherever it is possible, so that it can be easily walked around and a celebration toward the people can be carried out. (Emphasis added)
On 25 September 2000 the Congregation for Divine Worship and Discipline of the Sacraments issued a clarification (Prot. No. 2036/00/L) regarding #299 in the new Latin GIRM. That clarification says (emphases added):
The Congregation for Divine Worship and the Discipline of the Sacraments has been asked whether the expression in n. 299 of the Institutio Generalis Missalis Romani constitutes a norm according to which the position of the priest versus absidem [facing the apse (i.e. “ad orientem”)] is to be excluded. The Congregation for Divine Worship and the Discipline of the Sacraments, after mature reflection and in light of liturgical precedents, responds:
Negatively, and in accordance with the following explanation. […with an explanation of the Latin…]
The explanation includes different elements which must be taken into account. First, the word expedit does not constitute a strict obligation but a suggestion that refers to the construction of the altar a pariete sejunctum (detached from the wall). It does not require, for example, that existing altars be pulled away from the wall. The phrase ubi possibile sit (where it is possible) refers to, for example, the topography of the place, the availability of space, the artistic value of the existing altar, the sensibility of the people participating in the celebrations in a particular church, etc.
Look at it this way:
299. Altare maius exstruatur a pariete seiunctum, ut facile circumiri et in eo celebratio versus populum peragi possit, quod expedit ubicumque possibile sit.
299. The main altar should be built separated from the wall, which is useful wherever it is possible, so that it can be easily walked around and a celebration toward the people can be carried out.
That quod clause refers back to the whole first part “Altare… exstruatur… seiunctum”. It does not refer to celebratio (feminine) and it does not mean “because”.
The fine book by my friend Fr Uwe Michael Lang, Turning Towards The Lord, has a preface by Joseph Card. Ratzinger. Then Card. Ratzinger took up this very issue about the translation of paragraph 299 making it clear, with the Congregation, that (my trans. from the Italian edition):
“… the word ‘expedit‘ (‘is desirable’) required no obligation, but was a simple suggestion.”
Lang in his first chapter takes us through the genesis of that paragraph in the GIRM, pointing out also how it was applied, or rather misapplied, throughout the decades following the post-Conciliar reform for the liturgy. It is a very useful resource in itself.
There are any number of reasons why it might not be possible to separate an altar from the wall. For example, it might be that the altar is of historic importance. Maybe the architecture of the church is such that to change the altar would ruin the focus. It might be that there would not be adequate room in the sanctuary if the mensa (or table) of the altar was moved forward. Maybe in that place the decision was made to have celebrations of Mass ad orientem versus and not versus populum. All of these would be entirely adequate reasons.
You can probably think of more reasons yourself.
Furthermore, there is no obligation to change an existing altar. This would apply more to new construction.