What are constitutional conventions in Canada?

Constitutional conventions are unwritten rules of constitutional behaviour that supplement the written Constitution of Canada. Conventions are not enforceable by courts, but they bind the actors of constitutional government by political convention and by long usage. The Patriation Reference (1981) and the Reference re Secession of Quebec (1998) confirmed that constitutional conventions are essential to the operation of Canadian government, although they cannot be directly enforced through legal proceedings.

Major Canadian constitutional conventions include: the rule that the Governor General acts on the advice of the Prime Minister in nearly all matters (the foundation of responsible government); the rule that the Prime Minister leads the political party most likely to command the confidence of the House of Commons (which is usually the party with the most seats); the rule that ministers must be Members of Parliament (or, very rarely, senators); the confidence convention requiring the government to maintain confidence of the House of Commons; the rule that the government must resign or call an election if it loses a confidence vote; and the rule that the monarch's representative grants Royal Assent to any bill passed by Parliament.

Other conventions concern the operation of Cabinet and the provincial-territorial Lieutenant Governors and Commissioners. Cabinet solidarity (the rule that ministers publicly support Cabinet decisions or resign), Cabinet confidence (the rule that Cabinet deliberations remain confidential for at least 20 to 30 years), the appointment of ministers from the governing party caucus, the rotation of First Ministers' Meetings among host provinces, the federal disallowance of provincial laws (formally available under section 90 of the Constitution Act, 1867 but by convention not used since 1943), and many others operate by convention rather than by statute or constitutional text.

Constitutional conventions can change over time. The 1926 King-Byng Affair tested and ultimately confirmed the rule that the Governor General acts on the Prime Minister's advice on dissolution. The 2008 prorogation crisis tested but did not break the confidence convention. The 2016 Senate appointment reforms changed the convention of partisan Senate appointments. The federal Reform Act of 2014 codified some caucus conventions into statute. Conventions are particularly important in Canadian Westminster government because the written Constitution is incomplete; many of the fundamental rules of how government actually operates are not in the Constitution Acts of 1867 and 1982 but in conventions inherited from the British parliamentary tradition. The Patriation Reference noted that constitutional conventions are 'no less constitutional' than the written rules, even though courts cannot enforce them.