Legislature of Canada, created by the British North America Act .
The 301 members of its House of Commons are elected for maximum terms of five years from the provinces on the principle of representation by population. The 105 members of its Senate are appointed by Canada's governor-general from the regions of Canada and serve until age 75. The parliament has authority over the armed forces, regulates trade and commerce, levies taxes, and is in charge of banking, credit, currency and bankruptcy, criminal law, postal services, fisheries, patents and copyrights, the census, navigation and shipping, railways, canals, and telegraphs. It also retains powers not specifically assigned to provincial legislatures. The leader of the party winning the most seats in a general election becomes prime minister and is called on by the governor-general to form a government. He generally chooses elected party colleagues to form the cabinet . The party winning the second-largest number of seats in the House becomes the official opposition party.