Stare decisis — 'to stand by things decided' — is the discipline that turns individual judgments into a system of law. Vertically, every court is bound by the decisions of the courts above it in its hierarchy. Horizontally, courts follow their own past decisions unless there is strong reason to depart.
The doctrine trades flexibility for predictability: people can order their affairs, lawyers can advise, and like cases get like treatment. Final courts keep a safety valve — they may overrule themselves — but use it sparingly, because every departure unsettles what the rule of precedent exists to secure.
The Supreme Court of Canada binds all Canadian courts and will depart from its own precedents only where they prove unworkable or their foundations have eroded — and it has held that trial courts may revisit binding precedent in rare cases where new legal issues or significant changes in circumstances arise (Bedford, Carter).