THE COUNCIL OF NICEA
Here is my general understanding. If we are going to go into the context of religion then The Second Council Of Constantinople 553AD might be the place to study regarding reincarnation.
The council of Nicea/Constantinople were meetings between several bishops of Christian beliefs. In these meetings, the many bishops discussed, if not argued, about the divinity of Jesus and the trinity.
There was much debate and it took time, for the majority, to come to an agreement.
These meetings also decided who or what should be left out of the Christian doctrines, these were known as anathemas.
Anathema is given or charged against someone or something. If someone or something is charged with one or more anathemas, it means to be made an undesirable or unwanted.
If someone was charged with an anathema they could be said to be excommunicated.
In my research I have discovered a lot of debate and a lot of confusion, this bit is where it begins to get really murky/confusing, so, I will try to provide clarity on what happened.
In these meetings, the works of a man were discussed and or targeted, this man was a theologian called Origen (c184 AD - c253 AD) who argued for the pre-existence of souls (please see the pre-existence-of-the-soul link below).
Origen argued, or taught doctrine, that the soul exists before entering the body (that is in the womb) before the birth.
One of the main problems I have discovered is the lack of comprehensive understanding. When Origen argued or taught his doctrine of the pre-existence of the soul, was he describing what we consider reincarnation, his version, or was he being specific by saying the soul exists before entering into the flesh in the womb. Was pre-existence of the soul his version or definition of reincarnation? Take into account the fact that the word reincarnation didn't exist until 1829. This is where the problem lies. Is pre-existence of the soul another title, meaning, interpretation or name for reincarnation or not?
Research indicates that much of Origens work has been lost to time, so we might not be able to fully understand his works or meanings.
As I continued my studies, evidence suggests that a woman called Theodora (wife of Justinian I) influenced Justinian to make, or influence, huge fundamental changes to the people's beliefs.
One of the changes was to take out pre-existence-of-the-soul from the doctrines. Apparently, Origen's teachings or doctrines threatened the power of the establishment.
The aim/intention was Theodora doing what she can to become an all powerful woman with the hope of leaving a legacy behind after her death by being deified.
Before pre-existence was taken out of the doctrines, it was considered natural fact and accepted as a matter of fact.
So far, there is no solid concrete information that clearly states that pre-existence of the soul is actually reincarnation. It is very unfortunate that much of his work has been lost as it could have added clarity.
The definition of pre-existence of the soul might be, subjectively, linked to reincarnation but not definitively.
If, and it's a huge if, Origen's pre-existence-of-the-soul is meant to have been reincarnation then yes.......it was anathemitised. But, this can not, yet, be proven.
We need to be able to directly connect pre-existence-of-the-soul to reincarnation, only then can we say yes, the Council Of Nicea did anathematise reincarnation. Until then, no we can't.
Please refer to number 4 "Banning reincarnation" to understand the political intentions of Theodora and Justinian 1.
Please check the links below for further information. And check the books in the sources page for Origen's On First Principles book.
Credit/Source: The Reluctant Messenger | Wikipedia | Definitions.net
The Council's Issues Against Origen's doctrines
ORIGEN
Pre-existence Of The Soul
A definition of pre-existence
Definitions Of Pre-existence Of The Soul
Who Is Justinian?
Origen's On First Principles