This book develops the theory of the administrative act in procedures undertaken in administration and judicial proceedings of a legal and constitutional order before courts. Its principle source is the jurisprudence of the Colombian Constitutional Court and Council of State, which is compiled and analyzed from a doctrinal point of view. The text focuses on determining, through concrete cases, the legal and jurisprudential development of the administrative act, its classification, and the efficacy and validity of the sanctions of this figure. This study is accompanied with the legal development present in the administrative act compared to administrative claims, through which the text undertakes a study of the procedural prerequisites, compared with the legal development of revocation and administrative appeal. To this end, it analyzes the direct revocation, starting with the bases and descriptive study of this figure, and closes with the legal effects of the direct revocation. The second section develops the administrative action with respect to administrative dispute control mechanisms, in particular, those of invalidity, invalidity and restoration of the law, contractual, and direct reparation. The text goes into greater depth regarding State responsibility with respect to direct reparation, analyzing specific cases that serve to consider cases in which, in contrast to the administrative act, responsibility without state will due to omission, commission, or fact. The final part consists of a study of the effect of the administrative act on constitutional actions, which are described in relation to the exception of illegality and court review of the constitutionality and conformity with international conventions.