Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon CXX

Canon CXX.  (Greek cxxi.)

Of those who intrude upon peoples which they think belong to them, without the consent of those by whom they are held.

Item, it seemed good that whatever bishops seek the peoples whom they consider to pertain to their see, not by bringing their causes before the episcopal judges, but rush in while another is holding the place, all such, (whether said people are willing to receive p. 501 them or no) shall lose their case.  And whoever have done this, if the contention between the two bishops is not yet finished but still going on, let him depart who intruded without the decree of the ecclesiastical judges; nor let anyone flatter himself that he will retain [what he has seized] if he shall obtain letters from the primate, but whether he has such letters or has them not, it is suitable that he who holds and receives his letters should make it appear then that he has held the church pertaining to him peaceably.  But if he has referred any question, let the cause be decided by the episcopal judges, whether those whom the primates have appointed for them, or the neighbouring bishops whom they have chosen by common consent.

Notes.

Ancient Epitome of Canon CXX.

Let no one seize for himself what he thinks belongs to him:  but let the bishops judge or whom the Primate will give, or whom the neighbouring bishops shall give with his consent.  But whosoever has received letters from the primate concerning the keeping [of such regions and churches] merely deceives himself.

This is Canon xij. of Carthage, a.d. 418.