The binding legal principles established are: (1) The correct standard for certification of a class action is the "interests of justice" test under section 173 of the Constitution. (2) The factors identified in Children's Resource Centre (identifiable class members, triable cause of action, common issues of fact or law, suitable representative) are relevant considerations but not rigid prerequisites that must all be satisfied before certification can be granted. (3) Courts must apply these requirements flexibly, guided by what the interests of justice demand in the particular circumstances. (4) An appellate court should interfere with a certification decision only if the court below did not act judicially in exercising its section 173 discretion, based the decision on wrong principles of law, or materially misdirected itself on the facts. (5) At the certification stage, courts should not prematurely dismiss claims as not legally tenable unless it is plain that the claim cannot succeed, particularly where the claim raises novel legal issues or the law is developing. (6) There is no requirement for "exceptional circumstances" before an opt-in class action can be certified. (7) Section 173 of the Constitution empowers superior courts to develop common law procedural rules, including those governing class actions, in the interests of justice.