Pittsburgh's unauthorized Latin Mass: the Sunday obligation, and what Quo Primum can and can't do

The Code of Canon Law says: "A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass" (CIC can. 1248 §1). The canon is broad. It doesn't say the Mass must be authorized by the local bishop, only that it is celebrated "in a Catholic rite".

Since 2021, using the 1962 Missal requires the diocesan bishop's permission: "it is his exclusive competence to authorize the use of the 1962 Roman Missal in his diocese, according to the guidelines of the Apostolic See" (Traditionis custodes art. 2). A Mass celebrated without that permission is therefore illicit (unlawful), and the bishop may rightly tell the faithful not to attend.

In Church law, "A later law abrogates, or derogates from, an earlier law if it states so expressly, is directly contrary to it, or completely reorders the entire matter of the earlier law" (CIC can. 20). Traditionis custodes (2021) declares the reformed books "the unique expression of the lex orandi of the Roman Rite" and gives each bishop "exclusive competence" to authorize the 1962 Missal (art. 1–2) (Traditionis custodes). As disciplinary law, that governs today, whatever Quo Primum said in 1570.

Traditionalists can point to Benedict XVI, who wrote in 2007 that the 1962 Missal "was never juridically abrogated and, consequently, in principle, was always permitted" (Letter of 7 July 2007). That supports the Missal's legitimacy. But Benedict made the point when he issued new rules for its use (Summorum Pontificum), not by relying on Quo Primum. And a later pope has since issued different rules.