A introduction of a limit on expenditure on political structures at federal level brought about by the New Tax Regime has already been subject to judicial review in the abstract, based on the alleged breach of the principle of separation of powers. The discussion also involves preserving the financial autonomy guaranteed by the Constitution to the judiciary and other institutions forming part of the control system. The case by the Federal Supreme Court of the meaning of the financial autonomy examined in that article provides criteria for the examination of constitutionality sought. The article also examines the allegation of violation of the separation of powers, considering its instrumental role in preserving constitutional values such as democracy, institutional efficiency and fundamental rights. The conclusion is that there is no sufficient substantive element to allow, on the basis of an indefinite clause such as the separation of powers, an apriotic proclamation of the unconstitutionality of the New Tax Regime. Only time can present, in terms of implementation, substantive elements that can support the attribution of unconstitutionality.