On 11th of December 1931 the Statute of Westminster became law giving complete legislative independence to Canada, Australia, New Zealand, South Africa, Ireland (Free State), and Newfoundland (not then part of Canada).

They now had full legal freedom except in areas of their choosing.

An Act to give effect to certain resolutions passed A.D. 1931. by Imperial Conferences held in the years 1926 and 1930. [11th December 1931.]

Statute of Westminster 1931

You can read more about it here and what the countries listed chose to do: Statute of Westminster 1931