Hi Craige, thanks for your question.
State laws cannot change federal laws in Australia.
The Australian Constitution describes the composition, role and powers of the federal Parliament. It sets out how the federal and state parliaments share the power to make laws.
Chapter 3 of the Australian Constitution outlines the establishment of the High Court of Australia and describes how it can resolve disagreements between the federal and state governments over their law-making powers. If a law is contested—challenged—it is up to the High Court to decide whether the Constitution gives the state or federal parliament the power to make this law.
On some matters the federal Parliament and the state parliaments may make laws about the same things, for example, roads and health. Section 109 the Australian Constitution states that if the federal Parliament and a state parliament pass conflicting laws on the same subject, then the federal law overrides the state law, or the part of the state law that is inconsistent with it.