Соответствующая норма
Practice Relating to Rule 161. International Cooperation in Criminal Proceedings
Section C. Extradition of own nationals
Brazil’s Law on the Legal Status of Foreigners (1980), as amended in 1981, states: “Extradition shall not be granted when: I- the person sought is Brazilian, except in case the nationality was acquired after the [commission of the] act which motivates the [extradition] request.” 
Brazil, Law on the Legal Status of Foreigners, 1980, as amended in 1981, Article 77(I).