II. The Nicene canons are unalterable and binding universally.
For my brother and fellow bishop Anatolius not sufficiently considering your Grace's kindness and the favour of my assent, whereby he gained the priesthood of the church of Constantinople, instead of rejoicing at what he has gained, has been inflamed with undue desires beyond the measure of his rank, believing that his intemperate self-seeking could be advanced by the assertion that certain persons had signified their assent thereto by an extorted signature: notwithstanding that my brethren and fellow bishops, who represented me, faithfully and laudably expressed their dissent from these attempts which are doomed to speedy failure.
For no one may venture upon anything in opposition to the enactments of the Father.' canons which many long years ago in the city of Nicæa were founded upon the decrees of the Spirit, so that any one who wishes to pass any different decree injures himself rather than impairs them. And if all pontiffs will but keep them inviolate as they should, there will be perfect peace and complete harmony through all the churches: there will be no disagreements about rank, no disputes about ordinations, no controversies about privileges, no strifes about taking that which is another's; but by the fair law of love a reasonable order will be kept both in conduct and in office, and he will be truly great who is found free from all self-seeking, as the Lord says, “Whosoever will become greater among you, let him be your minister, and whosoever will be first among you shall be your slave; even as the Son of Man came not to be ministered unto but to minister.”
And yet these precepts were at the time given to men who wished to rise from a mean estate and to pass from the lowest to the highest things; but what more does the ruler of the church of Constantinople covet than he has gained? Or what will satisfy him, if the magnificence and renown of so great a city is not enough? It is too arrogant and intemperate thus to step beyond all proper bounds and trampling on ancient custom to wish to seize another's right: to increase one man's dignity at the expense of so many metropolitans' primacy, and to carry a new war of confusion into peaceful provinces which were long ago set at rest by the enactments of the holy Nicene Synod: to break through the venerable Father.' decrees by alleging the consent of certain bishops, which even the course of so many years has not rendered effective.
For it is boasted that this has been winked at for almost 60 years now, and the said bishop thinks that he is assisted thereby; but it is vain for him to look for assistance from that which, even if a man dared to wish for it, yet he could never obtain.
Source: Letters (New Advent)