From a reader:
A person [a man] who WAS Catholic, baptized and confirmed in Latin Rite, left the Church and became Orthodox and was ordained in the OCA then latter returned to the Latin Rite Catholic Church, desires to serve as a priest in the Catholic Church. Is this possible since he is validly, albeit illicitly, ordained from the OCA. Or, since there was formal schism in becoming Orthodox, does this bar him from functioning as a priest in the Catholic Church even though he was formally received back into Her?
I seriously doubt it he would be able to function as a priest.
It is possible. It would, I believe, require the personal intervention of the Supreme Pontiff.
In all the cases I know of Catholics who leave the Church, are ordained outside the Church, and then want to return to the Church, the men are readmitted to the Church “ut laicus“, as if they were a lay person.
It would be a rare case where an exception would be made.
It is not impossible. But it would be rare.