Quo Primum was a disciplinary document
and I cannot for the life of me understand how people will take it as "dogmatic" or use it to argue that the Church has no right to regulate celebrations of the old Mass. Take for example this article from Zenit, on the legal force of Quo Primum:
Another correspondent writing from the Middle East offers the parallel case of the 1568 document "Quod a Nobis" which introduced the new Roman breviary two years before the new missal. This document contains many expressions similar to "Quo Primum" regarding, for instance, the perpetual force of law, the obligation of use in all places, and the total prohibition of adding or omitting anything.
Our reader then comments: "As you are undoubtedly aware, St. Pius X radically rearranged the ancient Roman Psalter and changed a few lessons for a few days, and provided contracted lessons, among other changes in 1913. Moreover, he forbade the use of the old Psalter. This clearly shows that he was not bound by the prescriptions issued in 'Quod a Nobis' and since these are similar to those of 'Quo Primum,' those must not be binding either.
"I have found using 'Quod a Nobis' more effective because the adherents to 'Quo Primum' argue that it is restricted to the Ordinary (either whole or from the Offertory to Last Gospel), or to the Temporale only (despite evidence in encyclicals like 'Grande Munus' to the contrary). Since the Psalter is the most fundamental part of the breviary, no such statement can be made with regard to 'Quod a Nobis.'"
Of course I favour more celebrations of the old Mass (per Cardinal Ratzinger's comments), but I really can sympathise with bishops who hold back the indult because of people who will end up creating trouble for them. When (and that's a big when) Pope Benedict relaxes restrictions on it, one of the messages that action will carry is that the old Mass belongs to the Roman Church, not just to sectarian and polemical interests. [updated] A hasty action will serve only to act against the future of the Missal of St Pius V, just like how the introduction of the New Rite was like. As Catholics, united under the Vicar of Christ, we can offer up our prayers for the Holy Father, so that he may have the wisdom to discern when the right time is. In all things, charity, understanding and patience.
updated 16 Nov 2006.