Thomas Aquinas

“ The accuser deserves the punishment of retaliation in compensation for the harm he attempts to inflict on his neighbor: but the punishment of disgrace is due to him for his wickedness in accusing another man calumniously. Sometimes the sovereign remits the punishment, and not the disgrace, and sometimes he removes the disgrace also: wherefore the Pope also can remove this disgrace. ”

“ Wherefore the accused, if innocent, may condone the injury done to himself, particularly if the accusation were made not calumniously but out of levity of mind. But if the accuser desist from accusing an innocent man, through collusion with the latter's adversary, he inflicts an injury on the commonwealth: and this cannot be condoned by the accused, although it can be remitted by the sovereign, who has charge of the commonwealth. ”

“ Reply to Objection 1: Nothing prevents a man being debarred by sin from doing what men are under an obligation to do: for instance from meriting eternal life, and from receiving the sacraments of the Church. ”

“ Now that which belongs to charity is a duty that man owes to all both of high and of low degree, both superiors and inferiors. Since therefore subjects should not accuse their superiors, nor persons of lower degree, those of a higher degree, as shown in several chapters (Decret. II, qu. vii) , it seems that it is no man's duty to accuse.
Objection 3: Further, no man is bound to act against the fidelity which he owes his friend; because he ought not to do to another what he would not have others do to him. Now to accuse anyone is sometimes contrary to the fidelity that one owes a friend ”

“ It would seem that the accuser who fails to prove his indictment is not bound to the punishment of retaliation. For sometimes a man is led by a just error to make an accusation, in which case the judge acquit the accuser, as stated in Decret. ”