These are from readings for a uni course. I believe the reading is from the Attorney-General's department's website.
"The Australian Constitution was passed as part of a British Act of Parliament in 1900, and took effect on 1 January 1901. A British Act was necessary because before 1900 Australia was merely a collection of six self-governing British colonies and ultimate power over those colonies rested with the British Parliament."
So for the first 120 years of settlement and Aboriginal Slaughter Australia was under British occupation and law. Having said that I believe at times European's (as they were called - as opposed to Natives) were punished for various massacres so there was some justice under the British.
Ok, and where does Britain fit into our current system?
"As well as being a federation, Australia is a constitutional monarchy. Under this system of government, as the term suggests, the head of State of a country is a monarch whose functions are regulated by a constitution. Australia's Head of State is Queen Elizabeth II. The concept of the Crown pervades the Constitution. For example the Queen is part of (Australian) Parliament, and is empowered to appoint the Governor-General as her representative. The executive power of the Commonwealth is vested in the Queen and is exercisable by the Governor-General as her representative."
So even thought the Crown doesn't interfere much anymore, legally it still can.