In democratic societies in the world that are governed by a constitutional and notable
system as a constitutional jurisdiction for constitutionality control intends a question
of legitimacy for a government as decisions of broad social impact for Judges without
democratic representativeness. The present work has as scope an analysis of the
institute of the amicus curiae, as a tool to foment the process of constitutional
interpretation within the judiciary and the impacts of the new Civil Procedure Code of
2015 (Law No. 13.105 / 2015) on this institute. To do so, it will be worth studying the
origin of the institute, its expression in other legal systems on comparative law and its
evolution in Brazilian law.