Encyclical ‘Mediator Dei’ of 1947…

Pope Pius XII on ‘Traditionis Custodes’:

The Authority of the Roman Pontiff over the Sacred Liturgy

In his landmark encyclical letter on the Sacred Liturgy, Pope Pius XII taught clearly and authoritatively:

The Church has further used her right of control over liturgical observance to protect the purity of divine worship against abuse from dangerous and imprudent innovations introduced by private individuals and particular churches. Thus it came about — during the 16th century, when usages and customs of this sort had become increasingly prevalent and exaggerated, and when private initiative in matters liturgical threatened to compromise the integrity of faith and devotion, to the great advantage of heretics and further spread of their errors — that in the year 1588, Our predecessor Sixtus V of immortal memory established the Sacred Congregation of Rites, charged with the defense of the legitimate rites of the Church and with the prohibition of any spurious innovation.