Constitutive statements are important institutional statements which radically differ from regulative statements in both structure and semantics, to the point that the Institutional Grammar provides a specific syntax to represent them. In this talk we will present the concept of constitutive rules (and constitutive acts) from a legal-theoretical point of view. The exact extension of the concept of constitutive statement is a highly debated topic in legal theory, and we will try to provide clear criteria for the identification of constitutive statements as distinguished from regulative statements and statements of fact. We will then attempt to outline a taxonomy of constitutive statements in the light of the Constitutive Functions identified in the Institutional Grammar 2.0 Codebook.