/summa/XP/XPII/XP_Q26:
We must now consider those who can grant indulgences: under which head there are four points of inquiry:
(1) Whether every parish priest can grant indulgences?
(2) Whether a deacon or another, who is not a priest, can grant indulgences?
(3) Whether a bishop can grant them?
(4) Whether they can be granted by one who is in mortal sin?