This review of the book by Professor Diego Lopez, La Teoria Impura del Derecho [The Theory of Impure Law], reveals some of the aspects that weaken his novel and significant thesis concerning the transformation of juridical theory in Latin America. Specifically, it shows how Lopez's particular appreciation of some of Kelsen's views undermines the example that he gives as an illustration of theoretical transformation in Colombia. The article's central tenet is that Lopez's formulation, which may be called the rule of approximation to the transnational theory of law, TTL, is based on a formalized and non-critical view of TTL. In doing so, Lopez falls into the same trap that he purports to reveal as a characteristic of local development and that, in accordance with a standard reading of TTL, should be considered incorrect.