Quote:
The doctrine of the reserved powers of the States was overturned in the famous case, Amalgamated Society of Engineers v Adelaide Steamship Co Ltd (Engineers Case),[4] in 1920. Since the Engineers case, the Commonwealth's constitutional powers have been interpreted as plenary powers, that is, powers that are unqualified by any implied reservation of powers to the States. Accordingly, it is more appropriate to refer to State and Territory areas of 'traditional responsibility', or State and Territory 'jurisdiction', rather than to refer to 'States' rights'.
What it boils down to is that the Federal govt is not limited to any specific areas of legislation by the Constitution and if they do limit themselves, it's not because they have to. They can do what they want. Which theoretically should be what we want them to, although that's obviously not always the case.