http://dx.doi.org/10.5007/2177-7055.2017v38n75p219 The article adresses the weight of principles theory, according to the contours drawn by the neoconstitutionalism. The weight of principles model has been suffering from solid and emphatic criticisms, since it submits the judicial discourse to a deep deficit of rationality and legitimacy, opening the way to a clear usurpation of the legislative authority by a theoretical model that allows the empire of subjective decisionism and judicial moralism. This leads to the need of establishing material and procedimental limits that are capable to ensure a rational application the system, wich is essential to legitimate and justify the decisions about the conflift of principles and interests.