NPNF2, Vol 15, p357, contains the following quotes from Hefele (A Roman Catholic scholar):
"Nearly a century later Pope Hadrian I. distinctly recognized all of the Trullan decrees in his letter to Terasius of Constantinople and attributes them to the Sixth Synod: "All the Holy Six Synods I receive with all their canons, which rightly and divinely were promulgated by them, among which is contained that in which reference is made to a lamb being pointed to by the precursor as being found in certain of the venerable images." Here the reference is unmistakably to the Trullan canon LXXXII."
"That the Seventh Ecumenical Council at Nice ascribed the Trullan canons to the Sixth Ecumenical Council and spoke of them entirely in the Greek spirit cannot astonish us, as it was attended almost entirely by Greeks. They specifically pronounced the recognition of the canons in question in their own first canon; but their own canons have never received the ratification of the Holy See."
Act 4 of the 7th Ecumenical Council, just to give one example of the use of the Quinisext canons at that council records the
"Some men who are painfully ignorant in regard to these canons are scandalized and blatantly say, "We wonder whether there really are canons of the Sixth Council." Let such men become conscious of the fact that the holy and great Sixth Council was convoked in the reign of Constantine against those who were asserting the energy and the will of Christ to be a signle energy and a single will, and that the bishops who attended it anathematized the heretics and stated clearly and emphatically the Orthodox faith, after which they left for home in the year fourteen of Constantine's reign. Thereafter, however, let it not be forgotten that... the same fathers gathered themselves together in the reign of Constantine's son Justinian and promulgated the aforementioned Canons, and let no one have any doubt about them. For those who signed their names in the reign of Constantine are the same ones who signed their names to the present paper in the reign of Justinian, as becomes plainly evident from the exact likeness of their respective signatures as written by their own hands. For it was incumbent on them after declaring an Ecumenical Council to proceed to promulgate also ecclesiastical Canons" (From The Rudder, p 289).
For reference, here is canon LXXXII of the Quinisext (Trullan) Council):
"In some of the paintings of the venerable icons, a lamb is inscribed as being shown or pointed at by the Precursor's finger, which was taken to be a type of grace, suggesting beforehand through the law the true lamb to us Christ our God. Therefore, eagerly embracing the old types and shadows as symbols of the truth and preindications handed down to the Church, we prefer the grace, and accept it as the truth in fulfillment of the law. Since, therefore, that which is perfect even though it be but painted is imprinted in the faces of all, the Lamb who taketh away the sin of the world Christ our God, with respect to His human character, we decree that henceforth he shall be inscribed even in the icons instead of the ancient lam: through Him being enabled to comprehend the reason for the humiliation of the God Logos, and in memory of His life in the flesh and of His passion and of His soterial death being led by the hand, as it were, and of the redemption of the world which thence accrues."
It should be noted that this canon of the Quinisext council played a key role in the 7th Ecumenical Council, and that this was an Ecumenical canon was the basis of one the most important arguments it made against the Iconoclasts, and there can be no doubt the understanding that the Quinisext Canons were the canons of the 6th Ecumenical Council were behind the wording of the first canon of the 7th Ecumenical Council:
"...we welcome and embrace the divine Canons, and we corroborate the entire and rigid fiat of them that have been set forth by the renowned Apostles, who were and are trumpets of the Spirit, and those both of the six holy Ecumenical Councils and of the ones assembled regionally for the purpose of setting forth such edicts, and of those of our holy Fathers. For all those men, having been guided by the light dawning out of the same Spirit, prescribed rules that are to our best interest."
Roman apologists often claim that the canons of the 7th Ecumenical Council were never accepted by the Pope, and so are not binding, however, when they are arguing with Protestants, they often turn around and argue that the canons of certain councils were in fact accepted by the 7th Ecumenical Council on the basis of it’s first canon and the quote from the acts of the council given above:
William Webster” “First of all, the Councils of Carthage and Hippo did not establish the canon for the Church as a whole.“
Art Sippo: “Wrong. The Seventh Ecumenical Council reaffirmed the Canons of these Councils as binding on the Universal Church as did the Council of Lyon”
Now, the only basis for Art’s claim here could be that the 1st Canon of the 7th Ecumenical Council affirmed the canons of the Quinisext council, which specifically listed the Council of Carthage as a local Council which was accepted on an Ecumenical level. But when I have made arguments with Art Sippo based on the canons of the Quinisext Council, I have been told that these were not accepted by the Pope, and when I have pointed out that they were accepted by the 7th Ecumenical Council, I have been told that those don’t count either, because the Pope never accepted them. Go figure.