Gregor Heimburg, the bitter critic of the papacy and of Nicholas of Cusa, is said to have taunted Cusanus, saying that because Cusanus was defeated in a lawsuit in Mainz, he turned from the practice of law to theology.1 Heimburg, a utriusque iuris doctor who rendered his legal services to both secular and ecclesiastical princes, was certainly versed in the legal literature of his time. But, as we shall see below, history does not seem to bear out his insinuation that disappointment and failure in the field of law led Cusanus to take up theology as his career. It is probably of little importance to ask whether Cusanus would have continued to work as a lawyer had he won the case in Mainz. We must note, however, that Cusanus is so well known as a theologian, cardinal, philosopher, and even as a scientist that we are apt to forget his early career as a canon lawyer in the service of the archdiocese of Trier. It is only recently that due attention began to be paid to the legal activities of Cusanus.2 The purpose of this paper is to throw light not only on his education and activities as a canon lawyer, but also on the role which he played in the disputed episcopal election of 1430 in the archdiocese of Trier.