As to why Maximos made oblique reference to the keys and the gates of hell, it might do well to remember that it was commonly held at the time that all bishops were the heirs of Peter, and all held the keys--but among the Churches, Rome presided in love, because of its auctoritas, not its potestas or jurisdiction--both of which were negligible outside of its own province.
Excellent reference to Augustus' power, btw.
On the office of the keys, an interesting proof-text on that comes the Vita of St. Shenoute, whose writings represent the height of the Coptic language but whose chief claim to fame came from his breaking his staff over Nestorius' head at Chalcedon. St. Shenoute's disciple St. Besa tells "One day our father Shenoute and Our Lord Jesus were sitting down talking together," a very common occurance according to the Vita," and the Bishop of Shmin [modern Akhmim, St. Shenouti's local bishop, and the diocese where Nestorius died in exile] came wishing to meet the abbot. When Shenoute sent word that he was too busy to come to the bishop, the bishop got angry and threatened to excommunicate him for disobedience:The servant went to our father [Shenouti] and said to him what the bishop had told him. But my father smiled graciously with laughter and said: 'See what this man of flesh and blood has said! Behold, here sitting with me is He who created heaven and earth! I will not go while I am with Him.' But the Savior said to my father: "O Shenoute, arise and go out to the bishop, lest he excommunicate you. Otherwise, I cannot let you enter [heaven] because of the covenant I made with Peter, saying 'What you will bind on earth will be bound in heaven, and what you will loose on earth will be loosed in heaven' [Matthew 16:19]. When my father heard these words of the Savior, he arose, went out to the bishop and greeted him."
"Besa, Life of Shenoute 70-72 (trans. Bell)."
Now this dates not only before the schism of East-West, and the Schism of Chalcedon, but nearly the Schism of Ephesus. Now Shmin is just a town in southern Egypt, and the bishop there just a suffragan of Alexandria. So it would seem to be odd if the interpretation of Matthew 16:19 that Pastor Aeternus promotes were the ancient one why this would be applied to a bishop far from Rome, in a land where St. Peter never founded any Church. But it makes perfect sense from the Orthodox interpretation of Matthew 16:19, and indeed, according to "the Catholic Encyclopedia," the overwhelming consensus of the Fathers:
"It is comparatively seldom that the Fathers, when speaking of the power of the keys, make any reference to the supremacy of St. Peter. When they deal with that question, they ordinarily appeal not to the gift of the keys but to his office as the rock on which the Church is founded. In their references to the potestas clavium, they are usually intent on vindicating against the Montanist and Novatian heretics the power inherent in the Church to forgive. Thus St. Augustine in several passages declares that the authority to bind and loose was not a purely personal gift to St. Peter, but was conferred upon him as representing the Church...signifies that the power to absolve was to be imparted through St. Peter to members of the Church's hierarchy throughout the world."
http://www.newadvent.org/cathen/08631b.htm Nihil Obstat. October 1, 1910. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York
Another element, which AFAIK, Fr. Patrick Reardon has been the first to draw attention to, stems from the fact that papal primacy proof text of Matthew comes from the Gospel associated with Antioch, while the Gospel associated with Rome-that of St Mark (the only link between St. Peter and Shmin)-climaxes (according to some) with the same pericope but without the proof-text.
To get back to the OP, under the old rules, a cardinal had the right to pull rank over "sui juris patriarch" even in his own patriarchate, as the bishop of Shmin over Archmanderite St. Shenoute did. Does this comport with the practice of the first millenium, particularly as the office of cardinal and the college of cardinals did not exist in the first millenium, but the office of patriarch did? And what does that say about trying to squeeze ecclesiology through the keyhole of Pastor Aeternus, which necessitates this jamming of the key of the patriarchate into that lock of the cardinalate?
