Hubert Treiber has established himself as one of the world’s leading scholars of Weber, in particular of his Sociology of Law. Especially, Treiber defends Weber’s decisive contribution to legal pluralism , comparable to Eugen Ehrlich’s, although from a quite different perspective. Indeed, it is not possible to analyse Weber’s distinction between state and non-state law (a central distinction for legal pluralism) without taking into consideration what he means, sociologically, by “law” on the one hand and by “the state” on the other. Weber’s ideal typical construction of social relations under the category “law” requires an Archimedean point, which is the formal rationality of law , closely associated, at the end of an historical development, with the efforts of legal abstraction and systematisation by the proponents of Pandectism in modern Germany. In the following text, linked to some of Treiber’s major works, the author addresses first Weber’s analysis of the rationalities of law, and then deals with the question of the plurality of law, as these two aspects are closely intertwined.