Section 99 of the Constitution Act, 1867

Section 99(1) guarantees security of tenure for the judges of the superior courts, "during good behaviour". This is a fundamental provision to ensure judicial independence.^{[9][10]: 319} The phrase comes from the English Act of Settlement of 1701,^[11] which provided that judges of the royal courts would hold their office quamdiu se bene gesserint (Latin: "as long as he shall behave himself well").^[12]

When the Constitution Act, 1867 was enacted, section 99 provided for life tenure for superior court judges. The only way a judge could be removed from office was by the joint address of the two houses of Parliament. This was changed in 1960, when the House of Commons and the Senate passed resolutions calling on the British government to introduce an amendment to create mandatory retirement at age 75. The Constitution Act, 1960 renumbered the original part of section 99 as sub-section (1), and added sub-section (2), which set the retirement age at 75.^[13] The provision took effect on March 1, 1961, meaning that any judge who was aged 75 or older on that date automatically lost their position.^{[14][10]: 321–323}

The Preamble to the Constitution Act, 1867 provides that Canada is to have a constitution "similar in principle to that of the United Kingdom". The Supreme Court of Canada has ruled that this phrase means that judicial independence, which is a basic principle of the British constitution, is also an unwritten constitutional principle in Canada. As a result, the federal government is constitutionally required to have an Independent commission to review proposals for judicial compensation.^[15]

Taken together, section 99(1) and section 100, which requires the federal government to pay the salaries of provincial superior, district and county courts, are constitutional guarantees for judicial independence. The two sections ensure that judges cannot be arbitrarily removed from office, and must have their salaries provided by the federal government.