This may be considered a myopic debate, but it pertains to the question whether or not the Church of Rome accepted the Canons of the Council of Trullo (i.e. the Quinisext Council). The ramifications of whether they did, or did not, will not be discussed in detail here. Rather, the history of whether they at one time were accepted will be.
Arguments In Favor of the Acceptance of Trullo’s Canons. The historical evidence that Rome accepted the Council of Trullo is extremely strong. Rome had one (questionable) legate (Basil of Gortyna, who also acted as a legate during Constantinople III; Price, The Canons of the Qunisext Council, p. 35) and 11 additional bishops in their jurisdiction attending (Sissius of Dyrrachion, Ibid., and 10 from East Illyricum, Ibid., p. 11). These aformentioned attendees signed onto the council. The preceding demonstrates that Rome had some element of participation in the council through representatives, even if it was relatively minimal.
The Liber Pontificalis (a source which was updated during the 8th century) notes that Pope Saint Gregory II appears to have accepted the Council. He went to Constantinople and questioned Emperor Justinian II (who had convened the Trullo) about the Council. After receiving “an excellent reply” from Justinian II, his earlier opposition to Trullo had vanished as the emperor “resolved every question.” (Ibid., p. 43; passage in question is dated to the 740s) This is corroborated by a letter between Gregory II and Patriarch Germanos I quoted during Nicea II. It explicitly quotes Canon 82 of Trullo as from “the assembly of the holy [fathers].” (Price, The Acts of the Second Council of Nicea, p. 330) It should be noted that Canon 82 forbade the depiction of Christ as a lamb (opting for the depiction of His incarnate hypostasis–i.e. as a human). Interestingly, this Canon was anti-Roman, as the Church of Rome had followed this practice. (cf Price, The Canons of the Qunisext Council, p. 23) The fact that Rome had actually ceased conducting this practice immediately after the Trullan Council, as evidenced by a fresco commissioned by Pope John VII (approx 706-707 AD) which deliberately avoided the lamb depiction in conformance with the aforementioned canon, additionally implies the acceptance of Trullo. (Ibid., p. 42)
The preceding may imply full acceptance of Trullo, but it is not explicit evidence of such. However, such explicit evidence soon makes itself apparent. During the Council of Nicea 2, Canon 1 explicitly accepts all “the divine canons…those composed by the holy apostles, the celebrated trumpets of the Spirit, those published by the six holy ecumenical councils and by the councils convened locally to issue such injunctions, and those of our holy fathers.” (Price, Nicea 2, p. 610) This canon of Nicea 2, accepted by the West, clearly affirms Trullo. First, the fifth and sixth councils did not have canons and so by invoking the canons of “the six holy ecumenical councils,” it would have to be referencing the introduction to the Trullan canons. In this introduction, it asserts it is providing the canons the fifth and sixth canons lacked. (Price, The Canons of the Quinisext Council, p. 73) Second, the criteria of Canon 1 of Nicea 2, in its affirmation of both local councils and “those of our fathers,” is clearly is a citation of Canon 2 of Trullo. Canon 2 explicitly lists exactly which local councils and fathers are at issue.
Why this canon alone does not solve the dispute of whether the West accepted the Trullan canons is a question that there is no good answer to. It is on the basis of this canon that Nedungatt (2010) observes, “Recent scholarship, however, has rescued it [Trullo] and placed it back in the canon of the ecumenical councils.” (“The Council in Trullo Revisited,” p. 661) He calls this a “scholarly consensus.” (Ibid., p. 662)
There is a good reason for this consensus on the basis of corroborating evidence surrounding Nicea 2. Pope Adrian I in two separate occasions had accepted the Trullan canons. In his Letter to Taurisius (JE 2449) it is stated that , “I also accept the work of the same holy sixth council with all the canons,” a statement found intact in both the Greek and Latin manuscripts. (cf Price, The Acts of the Second Council of Nicea, p. 176) On top of this, Adrian I in a letter directed to Charlemagne cites Canon 82 of Trullo and attributes it to the “holy sixth council.” (Price, The Canons of the Qunisext Council, p. 50)
The Latin tradition since Nicea 2 has affirmed that the Trullan canons were accepted by Rome. In so doing, this tradition in time reconciled its anti-Roman canons as disciplinary and only applicable to the local context in the East. While this is a questionable reconciliation, it is a plausible (re-)interpretation of the “excellent reply” given by Justinian II which was accepted by Gregory II. How so? Justinian II probably put forward a compromise that allowed both sides to save face by employing economia. This worked due to the Trullan canons having great leeway in their application, thanks to the 102nd canon. In effect, Rome would be able to canonically not apply canons they found objectionable. The Trullan canons, such as Canon 30, had already explicitly applied economia in contexts which would otherwise forbid Roman practices. (Ibid., p. 38-39)