The rejection derived from the loss of prestige Charlemagne had suffered at not being represented at the Council of Nicaea, which led him to consider the council unecumenical. The Council of Frankfurt possessed a memorandum about iconodulism, which had been produced previously by Frankish theologians on the order of Charlemagne concerning the Byzantine iconoclastic controversy: the Libri Carolini.
The rejection stemmed from Charlemagne's diminished prestige after being excluded from the Council of Nicaea, leading him to view it as non-ecumenical. The Frankfurt Council had a document on iconodulism, previously produced by Frankish theologians under Charlemagne's order concerning the Byzantine iconoclastic controversy: the Libri Carolini.