Original: Like the other Dominions, Australia gained legislative independence from the Parliament of the United Kingdom by virtue of the Statute of Westminster 1931, which was adopted in Australia in 1942 with retrospective effect from 3 September 1939.
Simplified: Like the other Dominions, Australia gained legislative independence from the Parliament of the United Kingdom through the Statute of Westminster 1931. This came into force in Australia in 1942, but back dated to 3 September 1939.