The Fourth Ecumenical Council.  The Council of Chalcedon 44Canon XXIX.

Canon XXIX. It is sacrilege to degrade a bishop to the rank of a presbyter; but, if they are for just cause removed from episcopal functions, neither ought they to have the position of a Presbyter; and if they have been displaced without any charge, they shall be restored to their episcopal dignity.

And Anatolius, the most reverend Archbishop of Constantinople, said: If those who are alleged to have been removed from the episcopal dignity to the order of presbyter, have indeed been condemned for any sufficient causes, clearly they are not worthy of the honour of a presbyter. But if they have been forced down into the lower rank without just cause, they are worthy, if they appear guiltless, to receive again both the dignity and priesthood of the Episcopate.

And all the most reverend Bishops cried out:

The judgment of the Fathers is right. We all say the same. The Fathers have righteously decided. Let the sentence of the Archbishops prevail.

And the most magnificent and glorious judges said:

Let the pleasure of the Holy Synod be established for all time.