Canon 915

Canon 915, one of the canons in the current Code of Canon Law of the Latin Church of the Catholic Church, forbids the administration of Holy Communion to those upon whom the penalty of excommunication or interdict has been imposed or declared or who obstinately persist in manifest grave sin:

Those who have been excommunicated or interdicted after the imposition or declaration of the penalty and others obstinately persevering in manifest grave sin are not to be admitted to holy communion.

The corresponding canon in the Code of Canons of the Eastern Churches, which binds members of the Eastern Catholic Churches, reads, "The publicly unworthy are to be kept from the reception of the Divine Eucharist".

Anyone aware of having committed a grave sin is obliged to refrain from receiving Communion without first obtaining absolution in the sacrament of Reconciliation. In addition, canon 1331 §1 of the Code of Canon Law forbids an excommunicated person, even one who has incurred a latae sententiae (automatic) excommunication, from receiving Holy Communion or any other of the sacraments of the Catholic Church. Also forbidden to receive the sacraments is anyone who has been interdicted. These rules concern a person who is considering whether to receive Holy Communion, and in this way differ from the rule of canon 915, which concerns instead a person who administers the sacrament to others.

Canon 915 is immediately followed by canon 916, which concerns the recipient of Holy Communion, not the minister administering it to that person: "A person who is conscious of grave sin is not to celebrate Mass or receive the body of the Lord without previous sacramental confession unless there is a grave reason and there is no opportunity to confess; in this case the person is to remember the obligation to make an act of perfect contrition which includes the resolution of confessing as soon as possible."

...
Wikipedia