St. Thomas Aquinas on Denying Communion

Because it appears some people need a refresher:

A distinction must be made among sinners: some are secret; others are notorious, either from evidence of the fact, as public usurers, or public robbers, or from being denounced as evil men by some ecclesiastical or civil tribunal. Therefore Holy Communion ought not to be given to open sinners when they ask for it. Hence Cyprian writes to someone (Ep. lxi): "You were so kind as to consider that I ought to be consulted regarding actors, [and] that magician who continues to practice his disgraceful arts among you; as to whether I thought that Holy Communion ought to be given to such with the other Christians. I think that it is beseeming neither the Divine majesty, nor Christian discipline, for the Church's modesty and honor to be defiled by such shameful and infamous contagion."

But if they be not open sinners, but occult, the Holy Communion should not be denied them if they ask for it. For since every Christian, from the fact that he is baptized, is admitted to the Lord's table, he may not be robbed of his right, except from some open cause. Hence on 1 Corinthians 5:11, "If he who is called a brother among you," etc., Augustine's gloss remarks: "We cannot inhibit any person from Communion, except he has openly confessed, or has been named and convicted by some ecclesiastical or lay tribunal." Nevertheless a priest who has knowledge of the crime can privately warn the secret sinner, or warn all openly in public, from approaching the Lord's table, until they have repented of their sins and have been reconciled to the Church; because after repentance and reconciliation, Communion must not be refused even to public sinners, especially in the hour of death. Hence in the (3rd) Council of Carthage (Can. xxxv) we read: "Reconciliation is not to be denied to stage-players or actors, or others of the sort, or to apostates, after their conversion to God."