Here a quick translation, intense work, I hope I left no mistakes.
I did not translate the footnotes (= references to councils, etc.)
DOCTRINAL DECLARATION FROM APRIL 15 AVRIL, 2012, WHICH MGR FELLAY SENT TO CARDINAL LEVADA
I
We plight to always be faithful to the Catholic Church and to the Roman Pontiff, Christ's vicar, successor of Peter and head of the body of bishops.
II
We declare that we accept the teachings of the Church's magisterium regarding matters of faith and morals, giving to each doctrinal statement the required degree of assent, according to the doctrine contained in item 25 of the Lumen Gentium dogmatic constitution of the Second Vatican Council (1).
III In particular:
1 We declare accepting the doctrine re. the Roman Pontiff and the College of bishops, with its head, the Pope, as taught by the Pastor Aeternus dogmatic constitution of the first Vatican Council and by the Lumen Gentium dogmatic constitution of the Second Vatican Council, chapter 3 (De constitutione hierarchica Ecclesiæ et in specie de episcopatu), explained and interpreted by the Nota explicativa prævia to this very chapter.
2 We recognize the authority of the Magisterium to which only is entrusted the task of authentically interpreting the Word of God written or transmitted (2) in faithfulness to the Tradition, remembering that « the Holy Spirit was not promised to Peter's successors so that they may make known, under his revelation, a new doctrine, but so as to, with its assistance, they may saintly keep and faithfully express the revelation handed over by the Apostles, i.e. the deposit of faith » (3).
3 The Tradition is the living transmission of the Revelation « usque ad nos » (4) and the Church in its doctrine, in its life and in its cult, perpetuates and transmits to all generations what it is and all what it believes. The Tradition progresses within the Church with the assistance of the Holy Spirit (5), not as a contrary novelty (6) but by a better understanding of the depositum fidei (7).
4 The entire Tradition of the Catholic faith must be the criterion and the guide for understanding the teachings of the Second Vatican Council, which in turn illuminates – i.e. deepens and further clarifies– some aspects of the life and of the doctrine of the Church, implicitly presents in its midst or not yet conceptually formulated (8).
5 The statements of the Second Vatican Council and of the later pontifical magisterium re. the relationship between the Catholic Church and the non-Catholic Christian confessions, also re. the social duty of of religion and the right to religious freedom, whose formulation is difficult to reconcile with the former doctrinal statements of the Magisterium, must be understood in the light of the entire and uninterrupted Tradition, in a manner consistent with the truths previously taught by the Church's magisterium, without accepting any interpretation of these statements which may lead to expound the Catholic doctrine in opposition or in rupture with the Tradition and with this Magisterium.
6 This is why it is legitimate to promote by a legitimate discussion the study and the theological explanation of expressions and of formulations of the Second Vatican Council and of the consecutive magisterium, in the case where it appears that they cannot be reconciled with the previous Church Magisterium (9).
7 We declare that we recognise the validity of the sacrifice of the Mass and of the Sacraments celebrated with the intent of doing what the Church does with the rites referred in the typical editions of the Roman Missal and the Sacramental Ritual legitimately promulgated by popes Paul VI and Jean-Paul II.
8 By following the criteria set out above (III, 5), as well as canon 21 of the Code, we plight to respect the Church's common discipline and the ecclesiastical laws, especially those contained in the Code of canon law promulgated by pope John-Paul II (1983) in the code of canon law of the Eastern Churches promulgated by the same Pontiff (1990), reserving the right of a discipline to be conceded to the Society of Saint Pius X by a particular law.
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On lit en note :–
(1) Cf. aussi la nouvelle formule de la Profession de foi et du Serment de fidélité pour assumer une charge exercée au nom de l’Eglise, 1989 ; cf. CIC cann 749 ; 750, 1et 2 ; 752 ; CCEO cann. 597 ; 598, 1 et 2 ; 599.
(2) Cf. Pie XII, encyclique Humani Generis.
(3) Vatican I, Constitution dogmatique, Pastor aeternus, Dz. 3070.
(4) Concile de Trente, Dz. 1501 : « Toute vérité salutaire et toute règle morale (Mt. XVI, 15) sont contenues dans les livres écrits et dans les traditions non écrites qui, reçues par les Apôtres de la bouche du Christ lui-même ou transmises comme de la main à la main par les Apôtres sous la dictée de l’Esprit Saint, sont parvenues jusqu’à nous. »
(5) Cf. Concile Vatican II, Constitution dogmatique Dei Verbum, 8 et 9, Denz.4209-4210.
(6) Vatican I, Constitution dogmatique Dei Filius, Dz. 3020 : « Aussi doit-on toujours retenir le sens des dogmes sacrés que la sainte Mère l’Eglise a déterminé une fois pour toutes, et ne jamais s’en écarter sous le prétexte et au nom d’une intelligence supérieure de ces dogmes. Croissent donc et se multiplient abondamment, dans chacun comme dans tous, chez tous les hommes aussi bien que dans toute l’Eglise, durant le cours des âges et des siècles, l’intelligence, la science et la sagesse ; mais seulement dans le rang qui leur convient, c’est-à-dire dans l’unité du dogme, de sens et de manière de voir (St. Vincent de Lérins, Commonitorium, 28). »
(7) Vatican I, Constitution dogmatique Dei Filius, Dz. 3011 ; Serment antimoderniste, nº 4 ; Pie XII, Lettre encyclique Humani Generis, Dz 3886 ; Concile Vatican II, Constitution dogmatique Dei Verbum, 10, Dz. 4213.
(8) Comme par exemple l’enseignement de la sacramentalité de l’épiscopat in Lumen Gentium, nº 21.
(9) On trouve un parallèle dans l’histoire avec le Décret des Arméniens du Concile de Florence, où la porrection des instruments était indiquée comme matière du sacrement de l’Ordre. Néanmoins les théologiens discutèrent légitimement, même après ce décret, sur l’exactitude d’une telle assertion ; finalement la question fut résolue d’une autre façon par le pape Pie XII.