It has been disputed about whether such a deferral would constitute valid grounds under the constitution to trigger a double dissolution.

Section 57 of the Australian constitution governs the triggering of double dissolutions, and says:

If the House of Representatives passes any proposed law, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, and if after an interval of three months the House of Representatives, in the same or the next session, again passes the proposed law with or without any amendments which have been made, suggested, or agreed to by the Senate, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, the Governor-General may dissolve the Senate and the House of Representatives simultaneously. But such dissolution shall not take place within six months before the date of the expiry of the House of Representatives by effluxion of time.

The amendments that were produced from the Rudd-Turnbull deal have been introduced into the Senate, rather than the House of Representatives, so that if the Senate blocks the legislation or passes it with unacceptable amendments, it is the same legislation which has been amended as was blocked in August. If the House of Representatives had passed the deal’s amendments, however, the Senate would not trigger a double dissolution by blocking it.

Some analysts, such as Antony Green on PM today and on his blog, and Greens Senate chief of staff Ben Oquist on Twitter, have argued that a deferral of legislation to a Senate committee would not count as ‘failure to pass’ under Section 57.

Green argues that, while the 1951 double dissolution was caused by ‘failure to pass’ legislation, this took place after substantial delay. However, it seems unclear whether there are any minimum requirements for a ‘failure to pass’ argument, beyond the constitutional requirement that three months have passed between attempts to pass legislation.

On top of that, it appears that the only person the Government needs to convince to trigger a double dissolution is the Governor-General, who would be extremely unlikely to reject such a request. The only circumstances in which such an interpretation could be challenged in court would be if the CPRS legislation was passed in a joint sitting following a double dissolution election and another blocking of legislation by the Senate.

In such a case, any such overturning of legislation would not overturn the result of an election where Liberals were decimated and the Greens gained the Senate balance of power. According to Freehills law firm, it would not be possible to pass the CPRS through a joint sitting anyway, as it relies heavily on regulations, which could be subsequently disallowed by a Senate that had been circumvented in the passage of the legislation. This is the same reason why the Australia Card was not implemented after being the trigger for the 1987 double dissolution.

When considering these factors, it seems almost certain that the Government would be able to use the CPRS as a trigger for a double dissolution if it is referred to a Senate committee and the ALP decides to use the trigger.