Q. I will be attending a family wedding in an Orthodox church. May I receive Communion during the wedding Mass?
A. Canon 844, #2, says that, as often as necessity requires it or genuine spiritual advantage recommends it, and provided that the danger of error or indifferentism is avoided, the faithful, for whom it is physically or morally impossible to go to a Catholic minister, may receive the Sacraments of Penance, Eucharist and Anointing of the Sick from non-Catholic ministers in whose Churches these sacraments are valid.
Whatever else might be said, I think it would be very unlikely that a Catholic living in ordinary circumstances in a large city would find it physically or morally impossible to receive the Eucharist from a Catholic minister. Therefore I do not believe you may receive the Eucharist at an Orthodox wedding. Even if all the conditions seemed to be present, a Catholic might stop to ask or consider how members of the other Church might feel about a non-member receiving Communion in their Church.
