The BNA Act was enacted on 29 March 1867. It provided for the union of three colonies — the Province of Canada (Ontario and Québec), Nova Scotia and New Brunswick — into a federal state with a parliamentary system modelled on that of Britain.
Rupert's Land was acquired in 1870, and six provinces were added to the original four: Manitoba (1870), British Columbia (1871), Prince Edward Island (1873), Alberta and Saskatchewan (1905), and Newfoundland (1949).
The Act does not contain the entire Constitution of Canada. Complementing its text are British and Canadian statutes having constitutional effect (e.g., the Canada Elections Act) and certain unwritten principles known as "the conventions of the constitution." Conventions such as the power vested in the Crown to dissolve Parliament and call a general election are usually exercised on the advice of the prime minister.
Sharing of Powers
The Act outlines the distribution of powers between the central Parliament and the provincial legislatures. For example, section 91 gives Parliament jurisdiction over banking, interest, criminal law, the postal system and the armed forces; section 92 gives the provinces jurisdiction over property, most contracts and torts, local works, undertakings and businesses.
Because of the breadth or generality of the legislative powers conferred, occasionally a direct conflict arises between provincial and federal laws regulating the same things (e.g., security frauds). When such conflicts occur, federal law prevails. In the case of concurrent powers, exercisable by both jurisdictions, federal paramountcy prevails in matters involving agriculture and immigration (section 95), but provincial law prevails in old-age pensions (section 94A).
Unallocated powers such as aeronautics, radio, and official languages go to the federal government rather than to the provinces. The federal peace, order and good government power embraces these "residuary" areas and matters falling under "national dimensions" and "emergencies." "National dimensions" also signifies that certain matters — originally of a local nature and under provincial jurisdiction (e.g., day-to-day health care) — can, through altered circumstances, such as an epidemic, acquire a new aspect transcending provincial competence and thereby become subject to federal jurisdiction. In wartime, virtually all provincial powers may come under central control.
In 1976, the Supreme Court of Canada decided that Parliament also possessed what amounted to a peacetime emergency power to impose national wage and price controls to combat serious national inflation. Unlike the American constitution, which treats all states as equal, the Constitution Act,1867 contains no suggestion that all provinces are constitutionally equal. For example, the Prairie provinces, unlike the original four provinces of Confederation, did not possess rights to their lands and minerals for 25 years after becoming provinces.
Judicial interpretation has had a substantial effect on provincial and federal powers. Until appeals to Britain were abolished in 1949, influential judges on the Judicial Committee of the Privy Council often expansively interpreted provincial powers, such as those over property and civil rights, when they came into conflict with federal powers over peace, order and good government or the regulation of trade and commerce. The British judges sought thereby to offset the excessive centralism they perceived in the BNA Act (e.g., the federal veto over any provincial statute in section 90) and preserve a viable federal system.
Since 1949, the Supreme Court of Canada has pursued a more centralist interpretation. In 1980, the omission of a domestic amending formula in the BNA Act led to a constitutional crisis when Prime Minister Pierre Trudeau attempted unilaterally to patriate the Constitution from Britain without provincial consent. When the Supreme Court decided, in September 1981, that his proposal was unconstitutional in the conventional sense, Trudeau relented, with "patriation" finally being achieved in April 1982 by federal-provincial consensus.