Most 'class proceedings' are governed in Ontario by the Class Proceedings Act, 1992 (CPA, 1992), and federally by the Federal Courts Rules [R334.1-334.39] (under the Federal Court Act). They are a means of 'access to justice' by large groups of atomized plaintiffs (typically consumers) who would not - individually - be financially able to advance litigation against one or several related defendants (typically corporations) due to an imbalance of bargaining power. Recently there have been 'reverse' class proceedings, with large groups of atomized defendants - for example, internet users alleged to have breached copyright.
In this Isthatlegal class proceeding topic I index to sub-topics according to their class proceeding relevance - that is, both Ontario and Federal sub-topics are located together. This is because - as stated in Canada (Attorney General) v. Jost (Fed CA, 2020) [para 23] - the Ontario and the Federal (and BC too) class proceedings are similar so that a case in any of those jurisdictions has a good chance of being relevant to the others - particularly regarding the all-important certification phase.
In rare cases (typically involving unions), the Ontario Rules of Civil Procedure [RCP 12.07] allows for defendant representation separate from Ontario's Class Proceedings Act (CPA) (called a 'representation order') [see Civil Litigation - Class Proceedings].
RULES OF CIVIL PROCEDURE
The Rules of Civil Procedure [R12.01-12.06] have some procedural provisions that apply to the Ontario CPA. Civil Litigation - Class Proceedings [#]