In this paper we shall focus on an important class of constitutive norms, which we shall call source-norms, namely those norms establishing what norms, on basis of what properties, validly belong to a normative system. Institutions including their own source-norms - here called Self-Regulated Institutions - are able to incorporate dynamically and autonomously new (old) norms in their normative system. After describing these concepts, we shall present a formal model of source-norms built by exploiting the PRATOR system for defeasible argumentation and we shall try to apply it to electronic institutions.