This chapter sets out to establish a concept of legal certainty, defining legal certainty as a guarantee of observance founded on the paradigm of semantic-argumentative controllability. Such control, it is argued, depends on elements, dimensions and aspects to be jointly assessed. Accordingly, legal certainty entails processes of determination, legitimation, argumentation and justification that assure the semantic-argumentative controllability of state action, on one hand, and the respectability of the individual's law-based actions on the other, as well as reflexively grounding the argumentation referring to such actions.