The Statute of Westminster, of 11 Dec 1931, was a British law clarifying the powers of Canada's Parliament and those of the other Commonwealth Dominions. It granted these former colonies full legal freedom except in those areas where they chose to remain subordinate to Britain.

Desire for Autonomy

Previously the British government had certain ill-defined powers, and ultimately overriding authority, over legislation passed by the Dominions — Canada, Australia, New Zealand and South Africa. Things began to change after the First World War, in which the sacrifices of Canada and other Dominions on European battlefields had stirred feelings of nationhood, and desires for greater autonomy from the mother country.

Canada began to assert its independence in foreign policy in the early 1920s: When the government of Prime Minister William Lyon Mackenzie King refused to commit to assisting British occupation forces in Turkey without approval of Parliament in Ottawa (see Chanak Affair); when it signed a fisheries treaty with the United States without British participation; and when it made plans to establish a Canadian embassy in Washington DC.

Imperial Conferences

The Imperial Conference of 1926 was a more formal step — giving initial legal substance to the Balfour Report declaration that same year, that Britain and its Dominions were constitutionally "equal in status." The subsequent 1929 Conference on the Operation of Dominion Legislation and the Imperial Conference of 1930 continued to work towards agreement on fundamental changes in the Commonwealth's complex legal system.

Gradual Change

Finally in 1931, at the request and with the consent of the Dominions, the Statute of Westminster was passed by the British Parliament, further clarifying and cementing the Dominons' legislative independence.

Yet some limits remained. After consultation between Canada's federal and provincial governments, the repeal, amendment or alteration of the British North America Acts, 1867-1930 — Canada's Constitution — was specifically excepted from the terms of the statute. The amendment of the Constitution remained exclusively the preserve of the British Parliament until passage of the Constitution Act, 1982.

Nor did Canada immediately take up all of its new powers under the Statute of Westminster. Not until 1949, for instance, did the Judicial Committee of the Privy Council, a British body, cease to be a final court of appeal for Canadians.