[Natural Law]

"Why did the participants of the Counsel of Nicea vote on matters of theology and belief?"

The Bishops who met at Nicea were all directly the product of Apostolic Succession and had the responsibility transferred to them by the laying on of the hands in a direct unbroken link through the Apostles to Jesus Himself. The same cannot be said for the PCA, but Circlecity's reasoning does legitimize the Magisterium, doesn't it.

[circlecity]

"The Bishops who met at Nicea were all directly the product of Apostolic Succession"

As are all regenerate Pastors.