Canada is a federation of 10 provinces and three northern territories (including the Nunavut territory formed in 1999). Under the British North America Act of 1867, which united the four original provinces of Québec, Ontario, Nova Scotia, and New Brunswick into one dominion under the name of Canada, the federation was provided with a powerful central government, which, besides its areas of exclusive authority, held residual authority in matters beyond the powers of local or private concern specifically assigned to the provincial legislatures. The British North America Act—which effectively served, together with a series of subsequent British statutes, as Canada's constitution—could be amended only by the British Parliament. In 1982, the British North America Act was superseded by the Constitution Act (or Canada Act), the principal innovations of which are the Charter of Rights and Freedoms and the provision for amendment. For passage, an amendment requires approval by the federal Parliament and the legislative assemblies of at least two-thirds of the provinces, which must hold an aggregate of at least half the population of all the provinces. However, when an amendment derogates from provincial rights, it will not apply in any province in which the legislative assembly dissented by majority vote. When such an amendment deals with education or other cultural matters, the federal government must pay compensation to any dissenting province, to make up for the funds that would have been transferred had the province accepted the amendment.
Under the Constitution Act, the British sovereign remains sovereign of Canada and head of state; for the most part, the personal participation of Queen Elizabeth II in the function of the crown for Canada is reserved to such occasions as a royal visit. The queen's personal representative in the federal government is the governor-general, appointed by the crown on the advice of the prime minister of Canada; the governor-general is usually appointed for a term of five years. Active executive authority resides in the cabinet, or ministry, headed by the prime minister.
The federal Parliament is made up of the House of Commons and the Senate. A new House of Commons, with 301 members as of 1999, is elected at least once every five years by all Canadian citizens and British subjects 18 years of age or older who have resided in Canada for at least 12 months prior to polling day. Representation by provinces and territories is based on population, ranging from one for the Yukon Territory to 99 for Ontario.
The leader of the party that wins the largest number of seats in a newly elected House of Commons is asked to form the government. The governor-in-council (cabinet), responsible for determining all important government policies and for securing the passage of legislation, financial measures, and administrative provisions, is chosen by the prime minister.
The 105 members of the Senate, or upper house, are appointed for life, or until age 75, by the governor-general on the nomination of the prime minister, with equality of representation for regional divisions. There are equal proportions of senators from the Maritime provinces, Ontario, Québec, and the western provinces. In October 1992, Canadian voters declined a constitutional amendment that would have made the Senate an elected body.