The procedures of the Senate provide for special majorities for two kinds of procedural motions. A motion to rescind an order of the Senate and a motion for the suspension of standing orders moved without notice require an absolute majority to be carried. In the past the standing orders provided for special majorities for other questions.
Since the standing orders were adopted in 1903 the question has been raised whether any provision for a special majority in the standing orders is unconstitutional. Such a provision may be contrary to section 23 of the Constitution, which strongly implies that all questions in the Senate must be determined by the simple majority prescribed by the section. Against this seemingly conclusive argument that any provision for a special majority is contrary to section 23, it has been argued that it is open to the Senate, having regard to section 50 of the Constitution, which provides for the Senate to make rules and orders for the conduct of its proceedings, to determine that particular questions should be determined by a special majority. This argument may have greater force in relation to procedural as distinct from substantive questions.
In 1968-69 a majority of the Senate, in effect, accepted the argument that requirements for special majorities are unconstitutional, and overturned the provisions in the standing orders for special majorities. Rulings by the President that motions to suspend standing orders without notice require an absolute majority were dissented from by the majority of the Senate, in accordance with standing order 198. The relevant standing orders, however, were not changed, and were subsequently adhered to and enforced. It has since been accepted by the Senate that those standing orders are in force. In relation to the requirement for an absolute majority for the suspension of standing orders, senators have used contingent notices of motion in order to circumvent that requirement.
No account is taken of any vacancy in the Senate in determining whether there is an absolute majority. In other words, an absolute majority remains a majority of the whole number of senators, 39 out of 76 senators, although there may be only 75 or fewer senators actually in office.