Australian territories are creatures of the Commonwealth government, and have no States rights. Some question whether in the case of the ACT it should even have a parliament except to set some sort of Guinness record for over-government.
However the Australian States have Constitutionally enshrined rights. Amongst them is the right to make legislation that even the Commonwealth can't entirely destroy.
Back before the current malaise struck the country, Australia had a vigorous Federation, with a series of legal cases going back almost to Federation itself relating to how much power the Commonwealth has over the States. Many of the cases involved Western Australia, including an attempt to secede and the question of how much autonomy an Australian State has.
Looking briefly at the USA, we see that the state of Arizona, suffering under the yoke of unbearable illegal immigration and receiving no relief from the corrupt Obama regime, took the step of passing State law effectively banning illegal immigrants from the State. The mechanisms and the legislation itself were completely non-controversial, in fact they are less draconian than US Federal provisions for border control. However, it became a socialist target for extreme persecution, especially from the neo-Marxist Obama and his camp followers. The Federal US administration has turned on one of its constituent states. This is a quiet and undeclared legalistic civil war.
Back to Australia, and the question is can an Australian state provoke a similar situation?
The Australian Constitution provides to the Commonwealth superior and all-inclusive powers. One of those powers is Defence. This should mean that the Commonwealth can strike down any Arizona-type laws a State passes in Australia, especially with a left-wing Court system to rubber stamp centralism.
However, not every State-Commonwealth law case goes the way of the Commonwealth. If say Western Australia, with its long separatist history, frames an anti- illegal immigrant law carefully enough, it would be able to hamper the blank cheque that the Commonwealth gives illegals. For example the massive Federal handouts can't be affected by a state, but a state can certainly legislate to take away all state benefits and entitlements of all kinds to anyone in receipt of a Commonwealth handout based on their immigration status. In other words, illegals can be covered by a non-discriminatory law that would apply to all of them as well as to anyone else who might be caught by its provisions.
Another simpler law would be "no Australian passport, no job".
A third simple law would be to enshrine in state law that non-citizens and illegals receive low priority medical and hospital treatment and Australian citizens, the people who pay for everything, get first use of all facilities.
If a state government has the will, it can fight the Commonwealth successfully. Even if the stacked deck of the legal system is against it, the state would swiftly win the debate in the never-ending PR war.
It could happen... WILL it happen?