Procedural consistency and material truth: limits and scope of ex officio evidence. Ruling ‘Argentine Chamber of Fireworks Companies (CAEFA) and Others v. Municipality of Paraná on Unconstitutionality Action (Art. 51 Inc. b. Law 8369)’

The analysis of the ex officio nature of evidence in Argentine judicial proceedings was presented as a topic of considerable doctrinal and jurisprudential debate. The discussion focused on the tension between the principle of consistency, the impartiality of the judge, and the search for material truth. Several authors argued that measures to better provide granted magistrates the power to incorporate ex officio evidence when the parties did not offer the necessary elements to decide, without this implying a violation of the equality of the litigants. In this sense, it was highlighted that these measures benefited both parties by placing them in the same situation of doubt or uncertainty. In the administrative sphere, two positions coexisted: one that considered ex officio evidence unnecessary in review proceedings, and another that justified it to ensure effective protection of rights. Legal scholars such as Peyrano defended the exceptional nature of its use, limiting it to very specific circumstances, while the General Environmental Law expressly enabled its application to guarantee the protection of constitutional rights. In comparative law, both the Inter-American Commission and Court of Human Rights and the European Court recognised the importance of ex officio evidence in environmental and fundamental rights matters. Argentine jurisprudence, for its part, endorsed its use in cases of social significance, prioritising health and the environment over purely formal arguments. In conclusion, ex officio evidence has established itself as a legitimate tool, capable of harmonising impartiality, consistency and effective judicial protection within the framework of a fair process.