Can. 544

When a priest from the group mentioned in can. 517, §1 or its moderator ceases from office as well as when one of them becomes incapable of exercising his pastoral function, the parish or parishes whose care is entrusted to the group do not become vacant. It is for the diocesan bishop, however, to appoint another moderator; before someone is appointed by the bishop, the priest in the group who is senior in appointment is to fulfill this function.