Source: https://www.fssp.org/en/motu-proprio-summorum-pontificum-of-pope-benedict-xvi/
Timestamp: 2019-04-19 14:48:36+00:00

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Since time immemorial it has been necessary – as it is also for the future – to maintain the principle according to which ‘each particular Church must concur with the universal Church, not only as regards the doctrine of the faith and the sacramental signs, but also as regards the usages universally accepted by uninterrupted apostolic tradition, which must be observed not only to avoid errors but also to transmit the integrity of the faith, because the Church’s law of prayer corresponds to her law of faith.’1General Instruction of the Roman Missal, 3rd ed., 2002, no. 397.
Among the pontiffs who showed that requisite concern, particularly outstanding is the name of St. Gregory the Great, who made every effort to ensure that the new peoples of Europe received both the Catholic faith and the treasures of worship and culture that had been accumulated by the Romans in preceding centuries. He commanded that the form of the sacred liturgy as celebrated in Rome (concerning both the Sacrifice of Mass and the Divine Office) be conserved. He took great concern to ensure the dissemination of monks and nuns who, following the Rule of St. Benedict, together with the announcement of the Gospel illustrated with their lives the wise provision of their Rule that ‘nothing should be placed before the work of God.’ In this way the sacred liturgy, celebrated according to the Roman use, enriched not only the faith and piety but also the culture of many peoples. It is known, in fact, that the Latin liturgy of the Church in its various forms, in each century of the Christian era, has been a spur to the spiritual life of many saints, has reinforced many peoples in the virtue of religion and fecundated their piety.
Many other Roman pontiffs, in the course of the centuries, showed particular solicitude in ensuring that the sacred liturgy accomplished this task more effectively. Outstanding among them is St. Pius V who, sustained by great pastoral zeal and following the exhortations of the Council of Trent, renewed the entire liturgy of the Church, oversaw the publication of liturgical books amended and ‘renewed in accordance with the norms of the Fathers,’ and provided them for the use of the Latin Church.
“It was towards this same goal that succeeding Roman Pontiffs directed their energies during the subsequent centuries in order to ensure that the rites and liturgical books were brought up to date and when necessary clarified. From the beginning of this century they undertook a more general reform.’2John Paul II, Apostolic Letter “Vicesimus quintus annus”, 4 December 1988, 3: AAS 81 (1989), 899. Thus our predecessors Clement VIII, Urban VIII, St. Pius X3St. Pius X, Apostolic Letter Motu propio data, “Abhinc duos annos”, 23 October 1913: AAS 5 (1913), 449-450; cf John Paul II, Apostolic Letter “Vicesimus quintus annus”, no. 3: AAS 81 (1989), 899., Benedict XV, Pius XII and Blessed John XXIII all played a part.
But in some regions, no small numbers of faithful adhered and continue to adhere with great love and affection to the earlier liturgical forms. These had so deeply marked their culture and their spirit that in 1984 the Supreme Pontiff John Paul II, moved by a concern for the pastoral care of these faithful, with the special indult ‘Quattuor abhinc anno,” issued by the Congregation for Divine Worship, granted permission to use the Roman Missal published by Blessed John XXIII in the year 1962. Later, in the year 1988, John Paul II with the Apostolic Letter given as Motu Proprio, ‘Ecclesia Dei’, exhorted bishops to make generous use of this power in favor of all the faithful who so desired.
Art. 4. Celebrations of Mass as mentioned above in art. 2 may – observing all the norms of law – also be attended by faithful who, of their own free will, ask to be admitted.
Art. 7. If a group of lay faithful, as mentioned in art. 5 § 1, has not obtained satisfaction to their requests from the pastor, they should inform the diocesan bishop. The bishop is strongly requested to satisfy their wishes. If he cannot arrange for such celebration to take place, the matter should be referred to the Pontifical Commission “Ecclesia Dei”.
Art. 11. The Pontifical Commission “Ecclesia Dei”, erected by John Paul II in 19885Cf John Paul II, Apostolic Letter Motu proprio data “Ecclesia Dei”, 2 July 1988, 6: AAS 80 (1988), 1498., continues to exercise its function. Said Commission will have the form, duties and norms that the Roman Pontiff wishes to assign it.
From Rome, at St. Peter’s, 7 July 2007, third year of Our Pontificate.

References: Art. 4
 art. 2

Art. 7
 art. 5
 § 1

Art. 11