Can all Catholics, be they Roman, Eastern, Orthodox Eastern, etc., receive Communion at a Roman Catholic Church? If so, are there any Catholics (Catholic denominations) that are excluded?
First, let’s start by clarifying some terms:
[list]Roman Catholic* can both refer to a Catholic who is in union with the Bishop of Rome (which means it can refer to Catholics of the Eastern rites that are in union with Rome), or it can more specifically refer to a Catholic who is a member of the Roman rite of the Catholic Church. Usually an Eastern Catholic is specifically referred to as an Eastern Catholic (or by the particular name of his rite, such as Byzantine, Maronite, etc.), but he is first and foremost a Catholic and can certainly receive Communion in a Roman-rite Catholic church.
[list]An Eastern Orthodox Christian is a member of a church that broke off from unity with the Bishop of Rome, and thus is not properly considered a Catholic at all. Under certain conditions (see the quote from the Code of Canon Law that follows), he may receive Communion in a Catholic church; but, generally speaking, such intercommunion is not approved of by the Orthodox churches and the Catholic Church advises that such Christians respect the eucharistic discipline of their own churches.
Catholic ministers may lawfully administer the sacraments of penance, the Eucharist, and anointing of the sick to members of the Eastern churches not in full communion with the Catholic Church, if they spontaneously ask for them and are properly disposed. The same applies to members of other churches which the apostolic see [the See of Rome] judges to be in the same position as the aforesaid Eastern churches so far as the sacraments are concerned (canon 844 § 3, Code of Canon Law
[list]There are other Christian groups, currently not in communion with the Bishop of Rome, that the Holy See has judged to be capable of the sacramental sharing outlined in canon 844 § 3. The guidelines for Communion by the United States Conference of Catholic Bishops (USCCB) names the AssyrianChurch of the East and the Polish National Catholic Church. As with Orthodox Christians, these Christians are not, properly speaking, Catholics, at this time (source).
[list]Other non-Catholic Christians are not permitted to receive the Eucharist in a Catholic Church except under the extraordinary conditions outlined in the following canon.
If there is a danger of death or if, in the judgement of the diocesan bishop or of the episcopal conference, there is some other grave and pressing need, Catholic ministers may lawfully administer these same sacraments to other Christians not in full communion with the Catholic Church, who cannot approach a minister of their own community and who spontaneously ask for them, provided that they demonstrate the Catholic faith in respect of these sacraments and are properly disposed (canon 844 § 4).
**Conclusion: **All Catholics may receive Communion, assuming they are properly disposed to do so; non-Catholic Christians are subject to conditions, some more or less extraordinary depending on the relationship of the individual Christian’s church to the Holy See.