This document aims to analyze and contrast the former - Law 8.666/93 - and the current - Law 14.133/2021 - basic legal framework of the procurement mechanism of the Brazilian legal system and analyze, from the Microeconomic perspective of efficiency, auction theory and information theory, points of attention and bottlenecks resolved and perpetuated by legal change. For this purpose, in addition to the in-depth critical examination of the legal apparatus that delimits the guidelines to be followed by a bidding process in both regulations, the main current scientific literature on the subject was also considered. At the end of the project, the information and syntheses elaborated are connected to conclude, in the light of the Economic Analysis of Law, about the apparent effectiveness of the changes made and discuss the points that still need to be adjusted.