Declaration of war by Canada

It is an exercise of the royal prerogative on the constitutional advice of the ministers of the Crown in Cabinet and does not require the direct approval of the Parliament of Canada, though such can be sought by the government.

[2] To assert Canada's independence from the UK,[3] as already established by the Statute of Westminster, 1931, the Cabinet decided to seek the approval of the federal Parliament to declare war.

[3] Though the Canadian Minister of National Defence, Norman Rogers, had been killed in a plane crash that day,[11] Prime Minister Mackenzie King still tabled a motion in the House of Commons, stating in it: Whereas Italy has declared her intention to enter the war on the side of Germany and against the allied powers; and Whereas a state of war now exists between the United Kingdom and France on the one hand and Italy, on the other; and Whereas at the outbreak of war the Parliament of Canada decided to stand at the side of the United Kingdom and France in their determined effort to resist aggression and to preserve freedom;

[17] At the UK's urging, the Canadian Cabinet the next day issued a royal proclamation declaring war on Finland,[17] Hungary, and Romania, three countries that had recently allied themselves with Nazi Germany.

Therein, the Prime Minister tabled motions for parliamentary approval of the declarations of war,[3] although permission from the legislators was not legally required.

Cabinet, then headed by Prime Minister Louis St Laurent, stated to the House of Commons that Canada would not declare war on North Korea, but would send military forces to participate in a collective police action, "under the control of the United Nations for the purpose of restoring peace to an area where an aggression has occurred," in keeping with the Charter of the United Nations, which Canada signed in 1945.

the National Defence Act was amended in 1950, by the Canadian Forces Act, to allow for the Crown-in-Council to put the Canadian Armed Forces into active service both when the country's security is threatened and when the country engages in collective action under the UN Charter, the North Atlantic Treaty, or other international defence arrangements.