The 1931 Statute of Westminster granted full legislative freedom to a handful of Dominions that had been part of the British Empire and then the Commonwealth.

The process started in earnest in 1926, with an Imperial Conference of the prime ministers of the various countries in London. Attending were these heads of state:

• Australia's Prime Minister Stanley Melbourne Bruce
• Canada's Prime Minister William Lyon Mackenzie King
• The Irish Free State's William Thomas Cosgrave, President of the Executie Council
• Newfoundland's Prime Minister Walter Stanley Monroe
• Joseph Gordon Coates, Prime Minister of New Zealand
• The United Kingdom's King George V and Prime Minister Stanley Baldwin

One prime result of the conference was the Balfour Declaration, named after the Lord President of the Council, former U.K. Prime Minister Arthur Balfour. That Declaration eased U.K. dominance over the Dominions, which had been chafing to various extents for a few decades, most notably during World War I, when the U.K. had gone to war primarily in Europe and put out the call for armed forces from the Dominions to fight "for king and country." The same issue had cropped up in the early 1920s, when Canadian Prime Minister King kept his country's troops out of a U.K. occupation of Turkey, and again when Canada negotiated a fisheries treaty with the United States but without the participation of the U.K.

Another bone of contention for some of the conference attendees was vagaries in merchant shipping laws.

In particular, the Balfour Declaration includes these words, referring to the Dominions:

They are autonomous Communities within the British Empire, equal in status, in no way subordinate one to another in any aspect of their domestic or external affairs, though united by a common allegiance to the Crown, and freely associated as members of the British Commonwealth of Nations.

The Declaration also provided for the gradual replacement of governors-general, who had functioned as de facto heads of state, with high commissioners. Canada in 1928 became the first Dominion to make this change.

One part of the Commonwealth not affected by the Balfour Declaration was India. The Declaration made specific reference to the Government of India Act 1919, which gave Indians more of a say in their representation and government, but India was not represented at the Imperial Conference.

Four years after the Balfour Declaration, the Dominion heads of state again met in London. George V was still the king, and Cosgrave still represented the Irish Free State, but all other representatives were different:

• Australia's Prime Minister James Scullin
• Prime Minister of Canada R.B. Bennett
• Newfoundland Prime Minister Richard Squires
• Prime Minister George Forbes of New Zealand
• Prime Minister J.B.M. Hertzog of South Africa
• U.K. Prime Minister Ramsay MacDonald

Significantly, also attending was William Wedgwood Benn, Secretary of State for India. None of what was decided at the conference pertained to India.

The 1930 conference resulted in an official report and set of recommendations, which Parliament duly included in a law the following year.

The Statute of Westminster 1931 continued the move toward autonomy begun in the Balfour Declaration, in effect removing the U.K. Parliament legislative power from the Dominions. Specifically, the Statute said this:

No Law hereafter made by the Parliament of the United Kingdom shall extend to any of the said Dominions as part of the law of that Dominion otherwise than at the request and with the consent of that Dominion.

The various Dominions affected by the Statute passed their own legislation approving the terms of the Statute, to varying degrees. Canada, Ireland, and South Africa did so right away. Australia followed suit in 1942, and New Zealand did so in 1947. Newfoundland became part of Canada in 1949.