Where parties before a court reference matters requiring consideration beyond the original conception of the case, this may engage the interests of third parties not before the court, potentially requiring their joinder. The question of joinder depends not on the nature of the subject-matter of the suit, but on the manner in which, and the extent to which, the court's order may affect the interests of third parties. Courts will order joinder to ensure all parties interested in the subject-matter of the dispute and whose rights may be affected are before it, to avoid multiplicity of proceedings and waste of costs. At appellate stage, where non-joinder issues arise after substantial time and costs have been invested, courts may adopt expedient procedural mechanisms to notify potentially affected parties and provide them opportunity to consent to be bound or participate, rather than requiring the matter to revert to first instance. This is particularly appropriate in test cases raising constitutional questions affecting concurrent national and provincial legislative competence that will impact similarly situated parties across multiple provinces.