Who are those who had the right of ijtihad and whose ijtihad...

Who are those who had the right of ijtihad and whose ijtihad was binding (hujjah) for the others? On what grounds have the others no right to go against their ijtihad? Evidently, to go into the details of each of these questions is outside the scope of this paper. However, it is necessary to mention some relevant points here: The position of…