The canons of the Ecumenical Councils are regarded within the Orthodox Church as universally authoritative, though not in a strictly constructionist sense. Their canons have often been repealed or revised by the decisions of local synods or even of later Ecumenical Councils. Nevertheless, their legislation is central to the Orthodox canonical tradition, and appeals to such canons are more frequently made than to any other source of canon law. (OrthodoxWiki)