Canon 915, one of the canons in the 1983 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. Wikipedia