Luna de Cuba said:
Pursuant to s51(xxxi) of the Constitution, the Commonwealth Parliament can make laws with respect to "the acquisition of property on just terms". "Property" is broadly defined, and would, doubtless, include precious metals. Would it ever happen? Guess we'll have to wait and see.
The key part of this section is
of which the Parliament has power to make laws
Whilst argueable, I would believe, that it would be against the Constitution to legislate the confiscation of legal tender.
Especially if the AG/AU is in legal tender coin form as per s115. As far as I am aware, legal tender cannot be rejected as a mode of payment, or indeed confiscated, especially if condoned and sanctioned by the Constitution. Just my musings