Canadian Constitutional Law/Sources of Constitutional law
Canada has both a "written" and "unwritten" constitution. Canada has a "written" constitution in that the country has several "constitutional" documents laying out the basic structure and powers of the government. The most important of these are the Constitution Act, 1867 (formerly known as the "British North America Act") and the Constitution Act, 1982.
Canada has an "unwritten" constitution in that there exist equally important traditions and principles on the basic structure and powers of the government which are not included in any "constitutional" document. An example of the "unwritten" constitutional concept is the office of the Prime Minister. While the Prime Minister of Canada is the most powerful office in the Canadian government, none of the Canadian "constitutional" documents even mentions the existence of a Prime Minister. The Prime Minister's job exists by virtue of tradition.
The Supreme Court of Canada summed up the "unwritten constitution" this way:
- The Constitution is more than a written text. It embraces the entire global system of rules and principles which govern the exercise of constitutional authority. A superficial reading of selected provisions of the written constitutional enactment, without more, may be misleading. It is necessary to make a more profound investigation of the underlying principles animating the whole of the Constitution, including the principles of federalism, democracy, constitutionalism and the rule of law, and respect for minorities. (Re: Secession of Quebec  2 SCR 217 headnote)
Canadian federalism means that the sovereignty of Canada is divided between two levels, or "orders" of government: federal and provincial. Each province has its own government, and the constitution gives the federal government certain powers and each provincial government certain powers. The division of powers is listed in Sections 91 and 92 of the Constitution Act, 1867. Section 91 lists the powers of the federal government, while section 92 lists the powers of the provincial governments.
The most important "unwritten" constitutional principle relating to federalism is that Canada has full sovereignty, that is, Canada can exercise all of the powers of an independent country. All of Canada's sovereignty can theoretically be exercised by either the federal or provincial governments; there is nothing that one or the other government cannot do. Another unwritten constitutional principle is that it is up to Canada's courts to decide which government has the power to do what, when the rules are unclear.
Reading the Constitution Act, 1867, the most important Constitutional document until 1982, the impression one would get is that Canada is not a democracy, but a colony ruled directly by a Governor appointed by the Queen of England. An elected legislature exists, but all of the laws of the legislature must be approved by the Governor and most executive decisions are made by the Governor and his or her Council.
This is because one of the most important constitutional rules of Canada is unwritten. It is called Responsible Government. The important aspects of responsible government are:
- The Governor must appoint his or her Council (aka. "Council of Ministers" or "Cabinet") from the political party with the most support in the legislature
- The Governor must choose the leader of the political party with the most support in the legislature as Prime Minister
- The Governor must act "on the advice of the Prime Minister" (i.e., the Governor must do whatever the Prime Minister says) or "on the advice of Council" (i.e., the Governor must do as instructed by Cabinet).
Therefore, whichever party wins the election gets the most seats in the legislature. Their party leader becomes Prime Minister. The Prime Minister tells the Governor who to appoint to the Cabinet, and then the Cabinet tells the Governor how to run the country. In this way, the Governor's position becomes completely ceremonial; sovereignty, which is technically exercised by the Queen through her Governor, is in fact exercised through elected officials.
Responsible government applies equally to provincial governments. Each province has a ceremonial Lieutenant-Governor, appointed by the Queen, who acts "on the advice" of the Premier (the provincial equivalent of the Prime Minister) and the provincial Cabinet.
Constitutionalism and the rule of law 
Constitutionalism means that the Constitution is supreme. Statutes passed by legislatures may not violate the constitution; any part of a statute that violates the constitution is null. The government is not free to disobey the constitutional rules when it suits them, be they written or unwritten.
The rule of law is a fundamental principle, not only of Canadian constitutional law, but of Canadian life. The stereotype of Canadians as straight-laced people who want everything done "by the book" suggests how seriously the country takes the rule of law. The Rule of Law principle is that the government may not act arbitrarily, but must act only according to the authority given them by the law. The law must, in turn, be valid according to the following criteria:
- It must be validly approved (i.e., passed according to the rules of the legislature and given "Royal Assent" by the Governor)
- It must be consistent with the constitution
- It must be possible to obey (this usually means that it cannot conflict with another law, it must be made public, it cannot be retroactive, etc., although judges sometimes make exceptions to these rules)
Respect for Minorities 
This constitutional principle has existed since the beginning of the Canadian legal system, although this has not always led to minorities being respected in practice. Nowadays, it is a principle that guides courts in interpreting things such as Aboriginal treaties and the place of French speakers in Canada.
The Royal Prerogative 
The royal prerogative are the powers given to the crown by the common law. These powers are unique to the crown and have no equivalent power to any one else. In modern times, the royal prerogative has fallen into disuse. The courts have held that there is no longer the prerogative power to legislate or administer justice, and there remains little of this power left. The prerogative exists primarily as a convention and is generally accepted as no longer being enforced by the courts.
The Constitution Act, 1867 was not meant to be a complete constitution for an independent country. In 1867, the territory of what is now Canada was broken up into several provinces of the British Empire. The Constitution Act, 1867 was simply a statute passed by the British Parliament to federate several of its provinces. The relations between the Empire and its Canadian colonies would remain the same: the Empire would still run Canada's foreign affairs, sign and ratify treaties on its behalf, and declare war in its name.
When Canada became an independent country, the powers that the British Empire exercised on Canada's behalf fell to the federal government. However, they were not powers that the Canadian Parliament (legislature) inhereited. Rather, they were powers that the Governor-General inherited. As stated above, the powers of the Governor-General are in fact exercised by the Prime Minister. Therefore, decisions on how to run Canada's foreign affairs, to sign and ratify treaties, and declare war are not decisions that the Parliament of Canada make. Rather, they are made directly by the Prime Minister and Cabinet.
Constitution Act, 1867 
The Constitution Act, 1867 was the product of negotiations between the top officials of four British colonies in North America: Canada, Nova Scotia, New Brunswick, and Prince Edward Island. They were discussing ways to deal with several common problems: the huge expenses of building rail and canal projects, worsening relations with the United States, and the unworkable political systems that made the colonies hard to govern. In the end, the provinces of Canada, Nova Scotia, and New Brunswick agreed on a plan to create a federation of four provinces (by dividing the former province of Canada into the provinces of Ontario and Quebec). They proposed legislation to the Imperial Parliament in London, which passed it. On July 1, 1867, the British North America Act came into effect, creating a new British colony, "the Dominion of Canada" (s.3).
The highlights of the British North America Act (a.k.a. "the BNA Act") were:
- A federal system: powers would be shared between a new federal government and a government in each province (s.91 and 92);
- The federal government would have vast powers in the Canada's most crucial financial and economic areas (currency, all forms of taxation, the debt, banks, interest, the building of interprovincial railways and canals) as well as other areas of "national" concern, such as aboriginals and their lands, and criminal law (s. 91)
- The provincial governments would generally have powers over local matters and areas that affected the common people: property rights, licenses, hospitals, cities, courts, government land; (s. 92)
- The capital of the new country would be Ottawa, on the Quebec-Ontario border; (s.16)
- The federal government would have a House of Commons: an elected legislature with representation from the provinces roughly equal to the size of their population; (s.37-40)
- The federal government would also have a Senate, with 24 representatives each from Ontario and Quebec and 12 representatives each from New Brunswick and Nova Scotia, the members of which would be chosen by the Governor (in fact, by the Prime Minister of Canada); (s. 21-36)
- The provincial governments would each have one elected legislative assembly; Quebec would also have an appointed Legislative Council; (s.69, 71, 88)
- The federal government could set up a general court of appeal for Canada and other courts for the "better administration of the laws of Canada", and appoint the judges; (s. 101)
- While the provinces were in charge of courts, the Governor (i.e., Prime Minister of Canada) had the power to appoint the judges to the most important provincial courts. (s.96)