St. Ambrose excuses himself for not having gone to the consistory when summoned, on the ground that in matters of faith no one but bishops could rightly judge, and that he was not contumacious because he would not suffer wrong to be done to his own order. And he adds that Auxentius would perhaps choose as judges either Jews or unbelievers, that is, persons hostile to Christ. He says further that he is willing to discuss the matters in dispute at a synod, and that he would have told the Emperor by word of mouth what he is now writing, but that his fellow bishops and the people would not suffer him to do so.
Ambrose, Bishop, to the most gracious Emperor and blessed Augustus, Valentinian.
Source: Letters (New Advent)