A reader writes:
In a conversation on-line with fellow Catholics, I was told that attending liturgy at an Orthodox church would not fulfill your Sunday obligation. Now, I was a bit surprised. I hadn’t planned to spend my Sundays down at the local Greek Orthodox church, but I’d thought that the reason one wouldn’t do that was because well, one’s a Catholic, and you shouldn’t be attending a schismatic church. But since the liturgy at an Orthodox church is the Mass, would attendance fulfill your Sunday obligation if you were in a position where you couldn’t get to a Catholic Church?
Under current law, Eastern non-Catholic liturgies do not fulfill the Sunday obligation. The Code of Canon Law provides that:
Can. 1248 §1. A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass.
This means that to fulfill one’s Suday obligation one needs to attend a Catholic Mass (either that of the Roman church or one of the Eastern churches sui iuris in communion with Rome, such as the Maronites, the Chaldeans, etc.). It will not suffice if it is merely a valid celebration of the Eucharist or even if it is an almost identical liturgy being used in a non-Catholic church.
Confusion on this point was raised by the 1967 Directory on Ecumenism, which allowed Catholics to occasionally fulfill their Sunday obligation with an Eastern non-Catholic liturgy, but this was later suppressed. It may be argued that the release of the 1983 Code (quoted above) suppressed it since it makes no exceptions after using the word "Catholic." (If it meant to allow Eastern non-Catholic liturgies it should have said something like "A person who assists at a Mass celebrated anywhere in a church where the sacrament of the Eucharist is valid satisfies the obligation of participating in the Mass."
Even if it were not suppressed by the 1983 Code itself, it definitely was suppressed by the 1993 Directory for the Application of Principles and Norms on Ecumenism, which states:
115. Since the celebration of the Eucharist on the Lord’s Day is the foundation and centre of the whole liturgical year, Catholics—but those of Eastern Churches according to their own Law—are obliged to attend Mass on that day and on days of precept. It is not advisable therefore to organize ecumenical services on Sundays, and it must be remembered that even when Catholics participate in ecumenical services or in services of other Churches and ecclesial Communities, the obligation of participating at Mass on these days remains.
The reader then writes:
Are there any other circumstances where it would be all right to fulfill your Sunday obligation in that manner?
No, it doesn’t work quite like that. If you really can’t reasonably get to a Catholic Mass then your Sunday obligation is simply in abeyance. You don’t have to go. You could go to an Eastern non-Catholic liturgy but it would not be in fulfillment of your Sunday obligation because on that Sunday you are simply not obligated.
For such circumstances the Code of Canon Law does have a recommendation (not an obligation) to make:
Can. 1248 §2. If participation in the eucharistic celebration becomes impossible because of the absence of a sacred minister or for another grave cause, it is strongly recommended that the faithful take part in a liturgy of the word if such a liturgy is celebrated in a parish church or other sacred place according to the prescripts of the diocesan bishop or that they devote themselves to prayer for a suitable time alone, as a family, or, as the occasion permits, in groups of families.