The choice wasn't undisputed, however, and the opposing candidate, Heinrich von Brakel, provost of Busdorf, received the bishop regalia from the king and confirmation from the archbishop of Mainz. But Oliver appealed to the Roman Curia for his rights.[4] And on April 7, 1225, he was finally confirmed as Bishop of Paderborn by Pope Honorius III. However, not being in his diocese but in the vicinity of the pope, he was made Cardinal Bishop of Sabina in September 1225, resulting in the diocese of Paderborn being declared vacant.