What was the Statute of Westminster of 1931?

The Statute of Westminster, 1931 (22 George V, c. 4) was a British statute passed by the United Kingdom Parliament on December 11, 1931 that gave Canada and the other Dominions full legislative independence from the British Parliament. The Statute applied to Canada, Australia, New Zealand, South Africa, the Irish Free State, and Newfoundland. After the Statute, Britain could not legislate for a Dominion except by that Dominion's express request, and Dominion legislation was no longer subject to British disallowance or to the doctrine of repugnancy with Imperial statutes.

The Statute codified the principles of the 1926 Balfour Declaration (named after Arthur Balfour, Lord President of the Council and former Prime Minister, who chaired the relevant committee at the 1926 Imperial Conference). The Balfour Declaration had stated that Britain and the Dominions were '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'. The 1929 Imperial Conference's Operations of Dominion Legislation Committee (chaired by South African judge Christiaan Beyers) drafted the legislative text that became the Statute of Westminster.

The Statute had several specific provisions. Section 2 provided that the Colonial Laws Validity Act of 1865 no longer applied to Dominions. Section 3 confirmed that a Dominion's parliament had full extra-territorial legislative power. Section 4 provided that no UK Act would extend to a Dominion as part of its law except at the request and with the consent of that Dominion. However, sections 7, 8, and 9 created exceptions for Canada (continuing British authority over constitutional amendments to the British North America Act of 1867), Australia (continuing constitutional limitations until adopted by the Australian states), and New Zealand (continuing until adopted).

The Canadian exception under section 7 reflected Canadian inability to agree on a domestic amending formula. The federal and provincial governments could not agree on how constitutional amendments should be made, particularly which provinces' consent would be required. The Statute therefore left Canada in the unusual position of having full legislative independence for ordinary statutes but continuing to require British Parliament action for constitutional amendments. This anomaly persisted until patriation by the Constitution Act, 1982, which added the Canadian amending formula and terminated the British Parliament's role in Canadian constitutional amendments. The Statute of Westminster is recognised as a foundation of modern Canadian sovereignty and is commemorated as Statute of Westminster Day (December 11) in some Commonwealth tradition.