British North America Acts in the context of "Parliament of the United Kingdom"

Canada has ten provinces and three territories that are sub-national administrative divisions under the jurisdiction of the Canadian Constitution. In the 1867 Canadian Confederation, three provinces of British North America—New Brunswick, Nova Scotia, and the Province of Canada (which upon Confederation was divided into Ontario and Quebec)—united to form a federation, becoming a fully independent country over the next century. Over its history, Canada's international borders have changed several times as it has added territories and provinces, making it the world's second-largest country by area.

The major difference between a Canadian province and a territory is that provinces receive their power and authority from the Constitution Act, 1867 (formerly called the British North America Act, 1867). Territories are federal territories whose territorial governments have powers delegated to them by the Parliament of Canada. Powers are divided between the Government of Canada (the federal government) and the provincial governments by the Constitution Act, either exclusively or concurrently. A change to the division of powers between the federal government and the provinces requires a constitutional amendment. A similar change affecting the territories can be performed unilaterally by the government or Parliament of Canada.

The Constitution Act, 1867 (French: Loi constitutionnelle de 1867), originally enacted as the British North America Act, 1867 (BNA Act), is a major part of the Constitution of Canada. The act created Canada, a federal country, and defines much of its structure, including the Parliament of Canada (composed of the monarch, the House of Commons, and the Senate), the executive, parts of the court system, and the division of powers between the federal government and the provinces. The act also created two new provinces, Ontario and Quebec, and set out their constitutions.

In 1982, with the patriation of the Constitution, the British North America Acts which were originally enacted by the British Parliament, including this act, were renamed the Constitution Acts. However, the acts are still known by their original names in records of the United Kingdom. Amendments were also made at this time: section 92A was added, giving provinces greater control over non-renewable natural resources.

Before 1982, modifying the Constitution of Canada primarily meant amending the British North America Act, 1867. Unlike most other constitutions, however, the Act had no amending formula; instead, changes were enacted through Acts of the Parliament of the United Kingdom (or "Imperial Parliament") called the British North America Acts.

Other Commonwealth countries had taken over the authority for constitutional amendment after the Statute of Westminster 1931, but at the time, Canada decided to allow the Parliament of the United Kingdom to retain the power "temporarily". Between 1931 and 1982, the federal government, on behalf of the House of Commons of Canada and the Senate, would issue an address to the British government requesting an amendment. The request would include a resolution containing the desired amendments, which in turn were always passed by the British Parliament with little or no debate.

The legal system of Canada is pluralist: its foundations lie in the English common law system (inherited from its period as a colony of the British Empire), the French civil law system (inherited from its French Empire past), and Indigenous law systems developed by the various Indigenous Nations.

The Constitution of Canada is the supreme law of the country, and consists of written text and unwritten conventions. The Constitution Act, 1867 (known as the British North America Act prior to 1982), affirmed governance based on parliamentary precedent and divided powers between the federal and provincial governments. The Statute of Westminster 1931 granted full autonomy, and the Constitution Act, 1982 ended all legislative ties to Britain, as well as adding a constitutional amending formula and the Canadian Charter of Rights and Freedoms. The Charter guarantees basic rights and freedoms that usually cannot be over-ridden by any government—though a notwithstanding clause allows Parliament and the provincial legislatures to override certain sections of the Charter for a period of five years.

Patriation is the political process that led to full Canadian sovereignty, culminating with the Constitution Act, 1982. The process was necessary because, at the time, under the Statute of Westminster, 1931, and with Canada's agreement, the British Parliament retained the power to amend Canada's British North America Acts and to enact, more generally, for Canada at the request and with the consent of the Dominion. That authority was removed from the UK by the enactment of the Canada Act, 1982, on March 29, 1982, by the Parliament of the United Kingdom, as requested by the Parliament of Canada.

A proclamation bringing the Constitution Act, 1982, into effect was signed by Elizabeth II, as Queen of Canada, Prime Minister Pierre Trudeau, and Minister of Justice Jean Chrétien on April 17, 1982, on Parliament Hill in Ottawa. The patriation process saw the provinces granted influence in constitutional matters and resulted in the constitution being amendable by Canada only and according to its amending formula, with no role for the United Kingdom.