Meyendorff on the reception of the Fifth and Sixth "Ecumenical" Councils in the West

... although the Quinisext is invested with “ecumenical” authority in the Byzantine Church tradition, it has never been received as such in the West. Actually, since it explicitly condemns several Latin liturgical and canonical practices, it already clearly implies an understanding of Church tradition and authority differing from that of the Latin Church. (John Meyendorff, Byzantine Theology, 82)

Are the fifth and sixth councils ecumenical? It seems that John Meyendorff does not think that the Western Church has ever received it as ecumenical. This is not to say that the West has not approved of parts of these councils, but I doubt they endorsed them wholly.