Canon 1111
§1 As long as they hold an office validly, the local Ordinary and the pastor can delegate to priests and deacons the faculty, even a general one, of assisting at marriages within the limits of their territory.
§2 To be valid, the delegation of the faculty to assist at marriages must be given to specific persons expressly. If it concerns special delegation, it must be given for a specific marriage; if it concerns general delegation, it must be given in writing.
One who has general delegation for marriages can subdelegate another priest or deacon in individual cases.
One who has received a special delegation for a determined marriage or marriages can subdelegate another priest or deacon to assist at the marriage. However, the power to subdelegate must be expressly conceded to him by the one delegating. The exact wording of Canon 137 is as follows:
§1 Ordinary executive power can be delegated both for a single act and for all cases unless the law expressly provides otherwise.
§2 Executive power delegated by the Apostolic See can be subdelegated for a single act or for all cases unless the delegate was chosen for personal qualifications or sub- delegation was expressly forbidden.
§3 Executive power delegated by another authority who has ordinary power can be subdelegated only for ordinary power in individual cases if it was delegated for all cases. If it was delegated for a single act or for determined acts, however, it cannot be subdelegated except by express grant of the one delegating.
§4 No subdelegated power can be subdelegated again unless the one delegating has expressly granted this.
Canon 1113
Before special delegation is granted, all those things which the law has established to prove free status are to be fulfilled.