catholic.com/library/Who_Can_Receive_Communion.asp
"Because Catholics believe that the celebration of the Eucharist is
a sign of the reality of the oneness of faith, life, and worship, members of those churches with whom we are not yet fully united are ordinarily not admitted to Communion. Eucharistic sharing in exceptional circumstances by other Christians requires permission according to the directives of the diocesan bishop and the provisions of canon law. . . . "
Possible exceptions
“Catholic ministers may licitly administer the sacraments of penance, Eucharist and anointing of the sick to members of the
oriental churches which do not have full Communion with the Catholic Church, if they ask on their own for the sacraments and are properly disposed. This holds also for members of other churches, which in the judgment of the Apostolic See are in the same condition as the oriental churches as far as these sacraments are concerned” (CIC 844 § 3).
Christians in these churches should, of course, respect their own church’s guidelines regarding when it would be permissible for them to receive Communion in a Catholic church.
The circumstances in which Protestants are permitted to receive Communion are more limited, though it is still possible for them to do so under certain specifically defined circumstances.
Canon law explains the parameters: “
If the danger of death is present or other grave necessity,** in the judgment of the diocesan bishop or the conference of bishops**, Catholic ministers may licitly administer these sacraments to other Christians who do not have full Communion with the Catholic Church, who cannot approach a minister of their own community and on their own ask for it, provided they manifest Catholic faith in these sacraments and are properly disposed” (CIC 844 § 4).
It is important to remember that, under the rubrics specified above, even in those rare circumstances when non-Catholics are able to receive Communion, the same requirements apply to them as to Catholics.
The U.S. bishops’ guidelines for receiving Communion state, “We also welcome to this celebration those who do not share our faith in Jesus Christ. While we cannot admit them to Communion, we ask them to offer their prayers for the peace and the unity of the human family.”
Because they have not received baptism, the gateway to the other sacraments, non-Christians cannot receive Communion. However, in emergency situations, they can be received into the Church via
baptism, even if no priest is present, and an extraordinary minister of Holy Communion may bring them Communion as Viaticum.
I think that covers it, and none of the examples so far posted in this thread apply as far as I can tell.