Jürgen Habermas tells us that he has been influenced by pragmatism in three areas of his intellectual development: epistemology, social theory, and political theory. In this essay I would like to include a further area of Habermas' intellectual development where one could likewise suppose the influence of pragmatism: the philosophy of Law. The presentation will be divided in two sections. First, I will focus specifically on Charles S. Peirce's epistemological contributions, as it is in this author that Habermas has searched for the basis of his theory of communicative rationality. Second, I will say something about Peirce's influences on Habermas' discursive- theoretical theory of Law, and present Karl-Otto Apel's proposal as a heuristic counterpoint. The theme here explored is the possibility of framing Habermas philosophy of Law in the pragmatist tradition that descends from Peirce. Certainly, the defense of a realist philosophical perspective in terms of normative validity places their theoretical framework in continuity, while at the same time, in conflict with recent pragmatist proposals in epistemology and the Law.