In July 2021, Pope Francis abrogated Summorum Pontificum with the motu proprio Traditionis custodes which established the new circumstances for celebration of the 1962 Roman Missal.

While these negotiations did not produce a regularization of the SSPX, they did induce John Paul II to issue a decree in 1984, Quattuor Abhinc Annos, providing a limited permission, or indult, to celebrate the traditional Roman Rite.

"[2] The Society of St. Pius X, whose founder Archbishop Marcel Lefebvre was excommunicated in 1988 following the Ecône Consecrations,[3] set permission to use the Tridentine Mass as a preliminary condition for engaging in any doctrinal dialogue with the Holy See.

[4] As is customary for papal documents, the motu proprio (which has no title) is referred to by its incipit, the opening words of the (Latin) original text: Summorum Pontificum.

The document superseded the letter Quattuor Abhinc Annos of 1984 and the motu proprio Ecclesia Dei of 1988, which had allowed individual bishops, under certain conditions, to establish places where Mass could be said using the 1962 Missal.

[6] Apart from celebration of Mass, Pope Benedict authorised parish priests to grant, "after careful consideration" and "if advantageous for the good of souls", permission to use the older ritual in the administration of Baptism, Marriage, Penance, and Anointing of the Sick.

[10] The motu proprio allows what some traditionalists would call the novelty of proclaiming the Scripture readings "also" in the vernacular language in Masses with a congregation,[11] and in the accompanying letter the Pope said that "new Saints and some of the new Prefaces can and should be inserted in the old Missal", a matter that he committed for study to the Pontifical Commission Ecclesia Dei.

The conditions for the use of the 1962 Missal previously in force were replaced by the following: In an interview on Vatican Radio, the then Cardinal President of the Pontifical Commission Ecclesia Dei Darío Castrillón Hoyos commented that "priests can decide, without permission from the Holy See or the bishop, to celebrate the Mass in the ancient rite.

[13] In his accompanying letter, Pope Benedict explained that his action was aimed at broadly and generously providing for the rituals which nourished the faithful for centuries and at "coming to an interior reconciliation in the heart of the Church" with Traditionalist Catholics in disagreement with the Holy See, such as the members of the Society of St. Pius X.

He stated that, while it had first been thought that interest in the Tridentine Mass would disappear with the older generation that had grown up with it, some young persons too have "felt its attraction and found in it a form of encounter with the mystery of the Eucharist particularly suited to them."

In view of fears expressed while the document was in preparation, he took pains to emphasize that his decision in no way detracts from the authority of the Second Vatican Council and that, not only for juridical reasons, but also because the requisite "degree of liturgical formation and some knowledge of the Latin language" are not found very often, "the Missal published by Paul VI and then republished in two subsequent editions by John Paul II, obviously is and continues to be the normal Form – the Forma ordinaria – of the Eucharistic Liturgy.

Benedict, who himself led discussions with the SSPX during his tenure as Prefect of the Congregation for the Doctrine of the Faith, gave as a reason for making the effort represented by his motu proprio the regretted fact that, "over the centuries ... at critical moments when divisions were coming about, not enough was done by the Church's leaders to maintain or regain reconciliation and unity" and "omissions on the part of the Church have had their share of blame for the fact that these divisions were able to harden."

However, he pointed out, in the same cover letter, that, "needless to say, in order to experience full communion, the priests of the communities adhering to the former usage cannot, as a matter of principle, exclude celebrating according to the new books.

"[15] After saying in his letter to bishops, with which he accompanied the motu proprio, that "in the movement led by Archbishop Lefebvre, fidelity to the old Missal became an external mark of identity", Pope Benedict added: "The reasons for the break which arose over this, however, were at a deeper level."

Due to this continuing appeal of the ancient form of the Mass across generational groups, it was felt that cases should no longer be decided on a case-by-case basis, and that instead the need had arisen for "clearer juridical regulation which had not been foreseen" in the past.

[26] The traditionalist Society of Saint Pius X (SSPX), which was consulted by Pope Benedict during the process, said in a statement of the SSPX Superior General Bernard Fellay that it "extends its deep gratitude to the Sovereign Pontiff [Benedict] for this great spiritual benefit" and "rejoices to see the Church thus regain her liturgical Tradition, and give the possibility of a free access to the treasure of the Traditional Mass ... (for those) who had so far been deprived of it".

It wishes that the "favorable climate established by the Holy See" will "make it possible to consider more serenely the disputed doctrinal issues" and that the decree of excommunication which still affects its bishops be withdrawn.

Fellay adds: "The letter which accompanies the Motu Proprio does not hide however the difficulties that still remain", then stated that the Society is eager "after the decree of excommunication which still affects its bishops has been withdrawn—to consider more serenely the disputed doctrinal issues.

[32] The American Jewish Committee (AJC) stated in a press release: We acknowledge that the Church's liturgy is an internal Catholic matter and this motu proprio from Pope Benedict XVI is based on the permission given by John Paul II in 1988 and thus, on principle, is nothing new.

We appreciate that the motu proprio actually limits the use of the Latin Mass in the days prior to Easter, which addresses the reference in the Good Friday liturgy concerning the Jews. [...]

However, it is still not clear that this qualification applies to all situations and we have called on the Vatican to contradict the negative implications that some in the Jewish community and beyond have drawn concerning the motu proprio.

It reaffirms the competence of the diocesan bishops in implementing the motu proprio, recalling that in the event of a dispute about the celebration in forma extraordinaria judgement falls to the Ecclesia Dei Commission.

It clarifies the concept of coetus fidelium (in short "group of faithful") stabiliter existens ("stable") whose desire to participate in the celebration of the forma extraordinaria must be welcomed and accepted by pastors.

This applies also to Seminaries, where future priests should be given proper formation, including study of Latin and, where pastoral needs suggest it, the opportunity to learn the forma extraordinaria of the Roman Rite.27.

[42][43][44][45] In February 2023, Pope Francis issued a rescript, clarifying that bishops must obtain authorization from the Holy See before granting permission for parish churches to be used for Eucharistic celebrations with the preconciliar rite and before allowing priests ordained after 16 July 2021 to use the 1962 Roman Missal.