This paper presents a study about the special legislative procedure for peace, popularly known as fast track, and its role in the Colombian political transition. This study faces the interpretation that the fast track was an ineffective mechanism for the legislative implementation of the Peace Agreement, and attempts to explain this through two points of analysis. First, it presents the difficulty of implementing the constitutional amendments that the Agreement needed without activating the constituent power, which made it necessary to make the Constitution more flexible in order to integrate the pillars of the Agreement into the Constitution. Second, it explores the concept of constitutional aporia, that is the logical difficulty of reform the constitution through the categories of original and derived constituent power, and their consequences on the rigidity and flexibility of the Constitution.