The Holy See's Ecumenical Directory of 1970/71

Sharing in Sacramental Life, especially the Eucharist a) Sharing in Sacramental Life with members of the various Eastern Churches 122. Between the Catholic Church and the Eastern Churches not in full communion with it, there is still a very close communion in matters of faith.125 Moreover, “through the celebration of the Eucharist of the Lord in each of these Churches, the Church of God is built up and grows in stature” and “although separated from us, these Churches still possess true sacraments, above all—by apostolic succession—the priesthood and the Eucharist...”.126 This offers ecclesiological and sacramental grounds, according to the understanding of the Catholic Church, for allowing and even encouraging some sharing in liturgical worship, even of the Eucharist, with these Churches, “given suitable circumstances and the approval of church authorities”.127 It is recognized, however, that Eastern Churches, on the basis of their own ecclesiological understanding, may have more restrictive disciplines in this matter, which others should respect. Pastors should carefully instruct the faithful so that they will be clearly aware of the proper reasons for this kind of sharing in liturgical worship and of the variety of discipline which may exist in this connection. 48 Directory for the Application ofPrinciples and Norms on Ecumenism 1993 123. Whenever necessity requires or a genuine spiritual advantage suggests, and provided that the danger of error or indifferentism is avoided, it is lawful for any Catholic for whom it is physically or morally impossible to approach a Catholic minister, to receive the sacraments of penance, Eucharist and anointing of the sick from a minister of an Eastern Church.128 124. Since practice differs between Catholics and Eastern Christians in the matter of frequent communion, confession before communion and the Eucharistic fast, care must be taken to avoid scandal and suspicion among Eastern Christians through Catholics not following the Eastern usage. A Catholic who legitimately wishes to communicate with Eastern Christians must respect the Eastern discipline as much as possible and refrain from communicating if that Church restricts sacramental communion to its own members to the exclusion of others. 125. Catholic ministers may lawfully administer the sacraments of penance, Eucharist and the anointing of the sick to members of the Eastern Churches, who ask for these sacraments of their own free will and are properly disposed. In these particular cases also, due consideration should be given to the discipline of the Eastern Churches for their own faithful and any suggestion of proselytism should be avoided.129 126. Catholics may read lessons at a sacramental liturgical celebration in the Eastern Churches if they are invited to do so. An Eastern Christian may be invited to read the lessons at similar services in Catholic churches. 127. A Catholic minister may be present and take part in the celebration of a marriage being properly celebrated between Eastern Christians or between a Catholic and an Eastern Christian in the Eastern church, if invited to do so by the Eastern Church authority and if it is in accord with the norms given below concerning mixed marriages, where they apply. 128. A member of an Eastern Church may act as bridesmaid or best man at a wedding in a Catholic church; a Catholic also may be bridesmaid or best man at a marriage properly celebrated in an Eastern church. In all cases this practice must conform to the general discipline of both Churches regarding the requirements for participating in such marriages.