First Council of Constantinople, Canon II

The bishops are not to go beyond their dioceses to churches lying outside of their bounds, nor bring confusion on the churches; but let the Bishop of Alexandria, according to the canons, alone administer the affairs of Egypt; and let the bishops of the East manage the East alone, the privileges of the Church in Antioch, which are mentioned in the canons of Nice, being preserved; and let the bishops of the Asian Diocese administer the Asian affairs only; and the Pontic bishops only Pontic matters; and the Thracian bishops only Thracian affairs.  And let not bishops go beyond their dioceses for ordination or any other ecclesiastical ministrations, unless they be invited.  And the aforesaid canon concerning dioceses being observed, it is evident that the synod of every province will administer the affairs of that particular province as was decreed at Nice.  But the Churches of God in heathen nations must be governed according to the custom which has prevailed from the times of the Fathers.

Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.