Well, up until Vatican II it was still allowable for civil authorities to choose which men became bishops in some places. So getting rid of bishops carried political clout, too.What ecumenical councils like the Council of Nicea say are norms of faith.
A bishop doesn’t have the right to contradict them. Pope Benedict once said that every month he removed a bishop from his position. But dealing with such a bishop hasn’t always been so easy. In earlier centuries there have been great battles in Catholicism involving bishops that reject the teaching of Church ecumenical councils, and it took many years to put an end to the views they espoused.
In view of such things, it really wouldn’t be accurate to say that a bishop can simply say something contradicting an ecumenical council and that’s it. In the end, such a bishop’s teaching will be deceased.
25 But Jesus called them to him and said, “You know that the rulers of the Gentiles lord it over them, and their great men exercise authority over them. 26 It shall not be so among you; but whoever would be great among you must be your servant, 27 and whoever would be first among you must be your slave; 28 even as the Son of man came not to be served but to serve, and to give his life as a ransom for many.” (Matthew 20:25-28)