Pope [St.] Celestine I, in  an epistle to John of Antioch, which is contained in Volume One of the  Council of Ephesus, ch. 19, says: “If anyone who was either  excommunicated or exiled by Bishop Nestorius, or any that followed him,  from such a time as he began to preach such things, whether they be from  the dignity of a bishop or clergy, it is manifest that he has endured  and endures in our communion, nor do we judge him outside, because he  could not remove anyone by a sentence, who himself had already shown  that he must be removed.” And in a letter to the clergy of  Constantinople: “The Authority of our See has sanctioned, that the  bishop, cleric or Christian by simple profession who had been deposed or  excommunicated by Nestorius or his followers, after the latter began to  preach heresy, shall not be considered deposed or excommunicated. For  he who had defected from the faith with such preaching, cannot depose or  remove anyone whatsoever.” (As quoted by St. Robert Bellarmine, De Romano Pontifice: On the Roman Pontiff, trans. by Ryan Grant [Mediatrix Press, 2015], p. 308)