The Brazilian Securities and Exchange Commission (CVM) is the entity responsible to Securities market s regulation. For this function is needed a wide range actions, such as the edition and promotion the compliance with rules about the economic activities carried out in the securities market, investigation of violations of these rules as well the application of penalties in the ending of an administrative proceeding. Some of these administrative violations should also be characterized as a crime into the Brazilian Law. It is irregular investments offering for the general public, use of inside information and types of fraud or price manipulation, always in issuing and trading securities. It is not uncommon to the definition of authorship, so serious that configures such a crime, to depend of data collection and analysis regarding financial activities from individuals or entities submitted to a CVM investigation. The possibility to collect data regarding financial activities had been submitted to the Brazilian Supreme Court of Justice (STF) in the light of article fith, item XII, of the Brazilian Federal Constitution, that establishes the Data Secrecy protection, but also provides its deviation, however by court order, in hypothesis and under the rules established for the criminal investigation or criminal proceeding s instructions. When looking at this reality, the present thesis intends to verify if the inapplicability of the secrecy that protects the financial activities from individuals or entities, called breach of banking secrecy, when intended to repel doubts about the authorship of serious offenses that are being investigated by CVM, is legally sustainable. Thus, it delineates an interpretation of the Brazilian Federal Constitution equally inspired in constitutional law universal principles and by the modern civil constitutional law european doctrine.