Objection 1: It would seem that those who are not priests cannot excommunicate. For excommunication is an act of the keys, as stated in the Sentences IV, Dist. 18. But those who are not priests have not the keys. Therefore, they cannot excommunicate.

Obj. 2: Further, more is required for excommunication than for absolution in the tribunal of penance. But one who is not a priest cannot absolve in the tribunal of penance. Neither, therefore, can he excommunicate.

On the contrary, Archdeacons, legates and bishops elect excommunicate, and yet sometimes they are not priests. Therefore, not only priests can excommunicate.

I answer that, Priests alone are competent to dispense the sacraments wherein grace is given: therefore, they alone can loose and bind in the tribunal of penance. On the other hand, excommunication regards grace not directly but consequently, insofar as it deprives a man of the Church’s prayers, by which he is disposed for grace or preserved therein. Consequently, even those who are not priests, provided they have jurisdiction in a contentious court, can excommunicate.

Reply Obj. 1: Though they have not the key of orders, they have the key of jurisdiction.

Reply Obj. 2: These two are related to one another as something exceeding and something exceeded (A. 1; Q. 24, A. 1) and consequently one of them may be within the competency of someone while the other is not.