5 History, tradition and abundant ecclesiastical institutions bear outstanding witness to the great merit owing to the Eastern Churches by the universal Church. The Sacred Council, therefore, not only accords to this ecclesiastical and spiritual heritage the high regard which is its due and rightful praise, but also unhesitatingly looks on it as the heritage of the universal Church. For this reason it solemnly declares that the Churches of the East, as much as those of the West, have a full right and are in duty bound to rule themselves, each in accordance with its own established disciplines, since all these are praiseworthy by reason of their venerable antiquity, more harmonious with the character of their faithful and more suited to the promotion of the good of souls.
Source: Orientalium Ecclesiarum (Vatican.va)