Does a heretical bishop automatically lose priesthood?

No, not until a synod deposes him. This is the point on which our line differs most sharply from the harsher party. The councils summoned Nestorius as a bishop, tried him as a bishop, and only their sentence unmade him. Chalcedon's formula for the deposed is exact: “deprived of the grace that belongs to the priesthood”, one is deprived of what one still had.

St Nikodemos, commenting on the Third Apostolic Canon, states the rule: the canons do not act of themselves; a synod must apply them. Neophytos Kausokalyvites presses the proof from Canon 1 of Ephesus: if the canon had already stripped the guilty man, why does it direct the neighbouring metropolitans to proceed “unto casting him out even from the rank”? One does not cast out a man already outside. The rival idea, grace departing automatically at the moment of heresy, is the Latin latae sententiae penalty, foreign to the Orthodox order in which judgment belongs to the Church acting synodically.

• καθαίρεσις, deposition, the constitutive synodical act that removes the priesthood.
• ἐνυπόστατος, subsistent, real, the state of the uncondemned hierarch's Mysteries.
• latae sententiae, the Western doctrine of automatic penalty, which the Orthodox critique rejects.

Acts of Chalcedon (the deprivation formula); Canon 1 of Ephesus with Neophytos' analysis; the Pedalion on Apostolic Canon 3; the article on defilement in this library.

Heretical bishops of the Arian and Iconoclast periods validly ordained men later received in their orders, impossible if heresy had already emptied their priesthood.

“If his sacraments are still real, communion with him must be harmless.” That does not follow, the next two lessons explain why real Mysteries can still be received unto judgment.

• Does “pollution” mean the sacraments become invalid?
• Defilement without invalidity, the full study