OS,
No intention of being obtuse here, just seeking to clarify the points made. I have often found that people give answers or comments without having adequte understanding of the question in the first place, so please bear with me as I ruminate on this subject.
It seems to me that the heart of the matter is whether or not there is any basis for believing that the GB has any authority or appointment of any kind from God and if so was it given to them exclusively and irrevocably.
Another example of authority is generally agreed to refer to secular governments.
(Romans 13:1-4) 13
Let every soul be in subjection to the superior authorities, for there is no authority except by God; the existing authorities stand placed in their relative positions by God. 2 Therefore he who opposes the authority has taken a stand against the arrangement of God; those who have taken a stand against it will receive judgment to themselves. 3 For those ruling are an object of fear, not to the good deed, but to the bad. Do you, then, want to have no fear of the authority? Keep doing good, and you will have praise from it; 4 for it is God’s minister to you for your good. But if you are doing what is bad, be in fear: for it is not without purpose that it bears the sword; for it is God’s minister, an avenger to express wrath upon the one practicing what is bad.By what process do these secular governments hold authority and do we have a divine mandate to be in subjection to them? Or the example you cited of the Sanhedrin. Does Jesus comment in Matthew imply the Jews should be subject in any way to that institution?
(Matthew 23:2-3) 2
"The scribes and the Pharisees have seated themselves in the seat of Moses. 3 Therefore all the things they tell YOU, do and observe, but do not do according to their deeds, for they say but do not perform.