This new rite alone is to be used unless approval of the practice of saying Mass differently was given at the very time of the institution and confirmation of the church by Apostolic See at least 200 years ago, or unless there has prevailed a custom of a similar kind which has been continuously followed for a period of not less than 200 years, in which most cases We in no wise rescind their above-mentioned prerogative or custom. However, if this Missal, which we have seen fit to publish, be more agreeable to these latter, We grant them permission to celebrate Mass according to its rite, provided they have the consent of their bishop or prelate or of their whole Chapter, everything else to the contrary notwithstanding.
All other of the churches referred to above, however, are hereby denied the use of other missals, which are to be discontinued entirely and absolutely; whereas, by this present Constitution, which will be valid henceforth, now, and forever, We order and enjoin that nothing must be added to Our recently published Missal, nothing omitted from it, nor anything whatsoever be changed within it under the penalty of Our displeasure.
We specifically command each and every patriarch, administrator, and all other persons or whatever ecclesiastical dignity they may be, be they even cardinals of the Holy Roman Church, or possessed of any other rank or pre-eminence, and We order them in virtue of holy obedience to chant or to read the Mass according to the rite and manner and norm herewith laid down by Us and, hereafter, to discontinue and completely discard all other rubrics and rites of other missals, however ancient, which they have customarily followed; and they must not in celebrating Mass presume to introduce any ceremonies or recite any prayers other than those contained in this Missal.
Furthermore, by these presents [this law], in virtue of Our Apostolic authority, We grant and concede in perpetuity that, for the chanting or reading of the Mass in any church whatsoever, this Missal is hereafter to be followed absolutely, without any scruple of conscience or fear of incurring any penalty, judgment, or censure, and may freely and lawfully be used. Nor are superiors, administrators, canons, chaplains, and other secular priests, or religious, of whatever title designated, obliged to celebrate the Mass otherwise than as enjoined by Us. We likewise declare and ordain that no one whosoever is forced or coerced to alter this Missal, and that this present document cannot be revoked or modified, but remain always valid and retain its full force notwithstanding the previous constitutions and decrees of the Holy See, as well as any general or special constitutions or edicts of provincial or synodal councils, and notwithstanding the practice and custom of the aforesaid churches, established by long and immemorial prescription – except, however, if more than two hundred years’ standing.