In my observation, the Orthodox bishops are sometimes autonomous sometimes not (sometimes abide by the rulings of certain Holy Synods and Patriarchs they regard as superiors, other times they reject their former superiors and go their own way), and there’s nobody in charge or even capable of policing intercommunion among the Orthodox bishops. Thus, they frequently move in and out of communion with each other.
My observations refer specifically to Eastern Orthodoxy, because I am less familiar with Oriental Orthodoxy.
I will give a few examples of EO Bishops moving in and out of communion with each other:
- The Old Believer schism within the Russian EOC.
Certain bishops and priests in the 17th century rejected the liturgical reforms promulgated by the Patriarch of Moscow and the Tzar, and broke communion with them. Later on the Old Believers had many more schisms among each other, and as a result numerous schismatic Old Believer Churches formed. Some of these do have bishops and priests with a valid apostolic succession (however others rejected priesthood altogether), but they are not in communion with the MP (Moscow Patriarch).
- The New Calendar - Florinist (Old Calendar) - Matthewite (Old Calendar) schism within the Greek EOC.
The short story of this is that the bishop of Florin city regarded the New Calendarists (the EP of Constantinople and Greek bishops who adopted the New Calendar around 1922) as potential heretics, and broke communion with them. Bishop Matthew, on the other hand, regarded both the New Calendarists as
actual heretics (as opposed to
potential heretics), and the Florinists as heretics as well, and broke communion with both of these groups. Thus, the Greek EOC schismed into 3 fractions, each one out of communion with each other: namely the “New Calendarists”, the Florinists, and the Matthewites. All three Churches in schism have valid apostolic succession, but they are out of communion with each other.
- The New Calendar - Old Calendar schism within the Romanian, Bulgarian, and other EO Churches.
The Old Calendar Romanian EOC is in communion with the other Old Calendar (Greek, Bulgarian, Serb, Russian) EOC, but not with the New Calendar Romanian EOC. Same thing with the Bulgarians. We have valid bishops with apostolic succession at both sides (OC and NC side), but they are out of communion with each other.
- The Moscow Patriarch breaking communion with the EP of Constantinople.
This happened in the mid-1990s, over a dispute regarding the Estonian EOC. They were out of communion with each other and the Moscow Patriarch stopped remembering the EP in the Diptychs. Later on, they mended their relations and came back into communion with each other.
- ROCOR breaking communion with the Moscow Patriarch.
ROCOR (Russian Orthodox Church Outside of Russia) believed that the MP has fallen into apostasy in 1927, and broke communion with the MP. They recently mended their relations and re-established communion in 2006.
- ROCOR out of communion with the Greek, Antiochian, Romanian EOC, in the USA.
ROCOR, being an Old Calendar Church, regarded all mainline New Calendar EOC (such as Greek, Antiochian etc) as heretics, and instructed its faithful not to attend and not to commune in the New Calendar Churches, except in grave necessity where an Old Calendar priest was not available.
- The Basilian Fathers (EO Bishops and priests with a Russian heritage) establishing full communion with the Catholic Church, and losing communion with mainline EOC such as the Greek and Antiochian.
The Holy Synod of the Basilian Fathers decided to re-establish full communion with Rome and with the Catholic Churches. But the Greek and Antiochian EOC are not happy with this, and I’m sure the reunited MP-ROCOR Russian EOC is even less happier.
- Various Ukrainian EOC out of communion with each other (and with Moscow).
There was a schism within the Ukrainian EOC after the Soviet Union fell apart in 1991. There’s a Ukrainian EOC headed by a Metropolitan, loyal to the Moscow Patriarch. And there’s another Ukrainian EOC with its own Patriarch, out of communion with the other Ukrainian EOC, and also out of communion with Moscow. Moscow does not recognize the legitimacy of this Kiew Patriarch, but the EP of Constantinople does.
- A similar schism in Estonia.
There’s a Moscow-independent Estonian EOC recognized by the EP, however this is not recognized and it’s out of communion with the MP. And there’s of course another Estonian EOC loyal to Moscow, out of communion with the Moscow-independent faction.
- The situation of OCA.
The Orthodox Church of America is recognized by Moscow, but not by the EP. I don’t know whether the EP is in communion or out of communion with the OCA.
- The situation of the Japanese EOC.
There’s a certain Japanese EOC that claims independence from the EP and is recognized by the MP, however the EP does not recognize the Japanese EOC’s claim to independence. I don’t know whether the Japanese EOC and the EP are in communion or, in view of their dispute with each other, are they out of communion with each other.
There was a certain Catholic Cardinal responsible for inter-Church relations (maybe Cardinal Kasper but not sure of his name) who said, “we are increasingly aware that the EO Churches do not speak with one unified voice”. That makes it difficult for us Catholics to have a dialogue with them. But I guess a certain fragmentation, similar to that seen with Protestant denominations, is inevitable with the Eastern Orthodox Churches as a consequence of them having rejected the Pope as source of unity.