I would like to ask a question that came to my mind today. If a man was an orthodox Christian and he was married in the orthodox Church, then got divorced and became Catholic, would the sacrament of marriage in the Catholic church be available to him?
An Orthodox person married in the Orthodox Church would have a valid marriage unless proved otherwise by a marriage tribunal. On the surface the answer is NO that he is already married and not free to marry. If he were to present his case before a marriage tribunal and they were to find sufficient evidence that his marriage was not valid from the beginning, they would issue a decree of nullity, meaning that his marriage was not valid and he is free to marry in the Catholic Church.