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 142Canon CXIX.

That if a bishop shall possess a diocese which he has snatched from heresy for three years, no one may take it from him.

Item, it seemed good that if anyone after the laws should convert any place to Catholic unity and retain it for three years without opposition, it should not be taken away from him afterwards. If however there was during those three years a bishop who could claim it and was silent, he shall lose the opportunity. But if there was no bishop, no prejudice shall happen to the see, but it shall be lawful when the place that had none shall receive a bishop, to make the claim within three years of that day. Item, if a Donatist bishop shall be converted to the Catholic party, the time that has elapsed shall not count against him, but from the day of his conversion for three years he shall have the right of making a claim on the places which belonged to his See.