Research on the legitimacy of multi-stakeholder initiatives (MSIs) continues to thrive, however, the vague distinction between descriptive and normative legitimacy seems to cause growing confusion. In our paper, we identify three problems in the literature on MSI legitimacy: lack of precision regarding which of the two forms is used; blurring of boundaries between them; and ambiguity of assessment when assessing MSI legitimacy with the help of fine-grained criteria. These three problems, we argue, are not only detrimental to construct clarity but (...) they can also lead to an erosion of normativity, by which we mean the increasing lack of normative grounding or (unintentional) deconstruction of the normative elements of legitimacy. We introduce a framework that addresses these three problems, ultimately demonstrating how scholars can use the concept of MSI legitimacy in a manner that enhances construct clarity and avoids erosion of normativity. (shrink)