The High Court's ratification of Workchoices as constitutional was a bad decision for many reasons. One of the issues raised by Paul Keating was that it allows central control over a minimum wage through legislation alone.

Workchoices gets its legitimacy as legislation through the appeal to employers being from constitutional corporations. From the Workplace Relations Amendment:

"Australian employer" means:

(a) an employer that is a trading corporation formed within the limits of the Commonwealth (within the meaning of paragraph 51(xx) of the Constitution); or

(b) an employer that is a financial corporation formed within the limits of the Commonwealth (within the meaning of paragraph 51(xx) of the Constitution); or ...

The relevant part of the Australian Constitution is Sect 51.xx which read narrowly is:

51.The Parliament shall, subject to this Constitution, have power to make laws for the peace, order, and good government of the Commonwealth with respect to: - ...

(xx.) Foreign corporations, and trading or financial corporations formed within the limits of the Commonwealth: ...

Which may seem cut and dried, but read broadly with other heads of power in the constitution is not, as industrial relations is mentioned explicitly as well:

(xxxv.) Conciliation and arbitration for the prevention and settlement of industrial disputes extending beyond the limits of any one State:

For this reason national control of industrial relations has gone to three referendums for constitutional amendment to xxxv - all of which have failed.

Originally the corporations power was read very narrowly with a 1909 case, but since the 1970s when the High Court doctrine changed from one of federalism, to the doctrine that the judicial branch has the capability to make the constitution a 'living and breathing document', otherwise known as judicial activism, the corporations power has been one of opening the floodgates.

Because the High Court decision ignores the inter-state requirement of xxxv, and trashes the federal character of the Australian Constitution, making it national - or unitary - then it is open to all manner of centralised industrial management with legislation alone - including minimum wage.

From the Keating interview:

Let me make this clear, the Liberals decided that they wouldn't use the conciliation and arbitration power.

Under that power of the constitution you always needed a commission who tested capacity to pay and comparative wage justice. They've now used the corporations power and the High Court for the first time as validated its use. That means a Federal Government can now legislate the wage and the conditions.

and:

The safety nets now are the National Wage Case and the National Wage Case has gone because the commission has gone. But the Government can have Mr Harper and the Fair Pay Commission, but it's got no commission power it's really the Commonwealth Government. That's the point I'm making. It's not me saying it, it's the High Court saying it.

The nation-state is devoluting into the market-state. Where the nation-state used to be this heavily capitalised intensive centralised structure which would throw money to the poor and slow regions to make them catch up to the achieving regions; the market-state follows the lines of communications and is decentrsalised with innovation happening on the edges and bubbling into the center.

Workchoices is an industrial era approach to industrial relations - and focuses on issues that globalisation have largely made irrelevant. The issue for Australia is that its heavy centralisation of industrial relations is a weakness - a political and structural weakness.