Brazilian Constitution of 1988, written in the middle of the democratization process, in the end of 80s, established some axes for the formulation of a criminal policy according to the new scenario. The text of the Constitution gives the directions of this policy, that can be resumed in the following senses: the fundamental guarantees of liberal inspiration; the opening of criminal law for the protection of collective and supraindividual rights, and the maintenance of the traditional and historical profile of criminal law. The work aims to analyze if the laws that were produced in criminal subject, after de democratization of the country, were oriented by the directions brought by Constitution. Equally, we intend to analyze the judicial interpretation of this law, especially by Brazilian Supreme Court – STF. With that in mind, we assumed that Legislature had difficulties in formulating a rational criminal policy to Brazil, during this period, because it stayed in the center of internal and external forces, from which the choices emerged in an antagonic and swinging way. In a situation of crisis of rationality in the law system, judiciary has increased its role, tending to a judicial activism, in a way that we can conclude that criminal policy has been determinated by STF, instead of Legislature. The theories behind this scenario of institutional tensions were reduced to a narrow space. The penal guarantism summarizes great part of the critical positions in Brazil, although its categories and principles don’t satisfy the needs for a new criminal policy in rational frames. Taking into consideration these two elected actors: Legislature and STF, we studied the legislation in penal subject and the evolution of the STF interpretation about some themes which represent the axes determined by Constitution. Over these substract, we tried to identify the connections with the theories behind. The conclusion around the lacks of rationality of Legislature, and moreover, the assumption that these lacks can’t be supplied entirely by Judiciary, without sacrifices in democratic system, as well as the conclusion that the adoption of guarantist standards don’t give us all the possible directions, lead us to outline some proposals on criminal policy, taking into account the necessity of improving the role of penal law, and to recover the levels of rationality.