This dissertation analyse the relationships between the paradigms argumentative and regulatory in the context of the brazilian State reformation, since 1988 s Constitution. The argumentation theories development is related to the judicial methodology based on argumentative rationality, or in the Aristotelian forms, as proposed by Chaïm Perelman, or in the procedural dimension, as Jürgen Habermas and Robert Alexy defend. Both perspectives increase the role of the law general principles, motivating all public decisions. In the same way, the crisis of the public administration legitimacy put in scene the very need of participation in the public decisions, increasing the public space strength and the efficiency of the State. These decisions are taken according to notions as proporcionality. The search for a legitimate, efficient and participatory public administration is related to the need of publicizing the administrative agents discourses, wich is assured by argumentative use of reason. Therefore, in the regulatory model, wich is being established, must be take account of the argumentatives principles and social partnership. The legitimacy imperative is the intersection point between the two paradigms, were the public administrator can start the building of an action more compromised and ethical.