(b) if the bill provides for the alteration of this section, Schedule I to this Constitution or any of the provisions of this Constitution or the Supreme Court Order specified in that Schedule, unless after it has been passed by the Senate and the House or, in the case of a bill to which section 50 applies, after its rejection by the Senate for the second time, the bill has been approved on a referendum, held in accordance with such provision as may be made in that behalf by Parliament, by a majority of the votes validly cast on that referendum.