This work addresses the conflict of competences between the three constituent powers of the modern state, arising from the issue of Resolution No. 22,610 of 2007, which deals with party infidelity. The question is whether there has been a violation of the constitutional principle of the separation of powers. The aim is to analyse the interference of the Judiciary in the competence of the Legislative Branch. The proposed investigation is of great importance for addressing the critical moment that Brazilian political life is experiencing, since the Judiciary, with the aim of strengthening party institutions, in a very controversial decision, granted a new interpretation to what the Constitution addressed, thus creating a new cause for loss of electoral mandate, a new cause for loss of elective office, now due to an act of party infidelity, an act that until then had not been contemplated in the current legal system, generating countless questions about the violation of the constitutional principle of the separation of powers, a principle that is the basis of the Brazilian Democratic State of Law.