And here is a very clear article by Father Edward McNamara (dated 2011-06-21), professor of liturgy at the Regina Apostolorum university citing all the relevent documents and private correspondance.
MASS WITH THE SOCIETY OF ST. PIUS X .
zenit.org/article-32905?l=english
His bottom line based on all the relevent documents::
I would say, therefore, that a conscientious Catholic should not knowingly attend a Mass celebrated by a priest not in good standing with the Church. Doing so deprives participation at Mass of that fullness of communion with Christ and his Church which the Mass, by its very nature and in all its forms, is called to express.
Therefore, the first thing to do would be to investigate the availability of Mass (in the ordinary or extraordinary form) in another locale during your visit. If it is not available, then you could attend any Eastern Catholic celebration.
Only if there is objectively no alternative should one attend the Mass celebrated by a priest from the Society of St. Pius X. If one has to do so, then I would say that one may go in good conscience.
Yes, this is exactly how it is. I am a supporter of the extraordinary form of the Roman rite, but we are not allowed to go to a Mass of the Society of St. Pius X if there are alternatives, including the ordinary form.
Every Catholic should know the extraordinary form! If you are lucky the Fraternity of Saint Peter or your diocese offers it. If the extraordinary form is not offered in your region or diocese, petition your pastor. Your pastor is required to offer the extraordinary form if there is sufficient interest from a stable group of parishioners. If this fails, petition your diocesan bishop. And if this also fails, the matter should referred to the Pontifical Commission Ecclesia Dei. As long as there is stable group of parishioners that is attached the extraordinary form, it is their right, according Summorum Pontificum, to have the extraordinary form available to them.