Separation of powers and external relations: the role of constitutional courts in judicial review of international treaties

The judicial control over the constitutionality of international treaties can affect the Executive in the conduct of foreign affairs. A negative court decision declaring a treaty to be unconstitutional can give rise to strong political and legal consequences. How constitutional courts behave in cases of constitutional review of international treaties? Is there a judicial activism or self-restraint in judging the compatibility of treaties with the national constitution? Based on a legal-comparative analysis between the Brazilian Federal Supreme Court and the Supreme Court of Argentina the paper will show that cases of control over the constitutionality of international treaties are rare and in general both courts consider the sensitive foreign policy interests involved when formulating their decisions. The comparison between Brazil and Argentine is justified by the similarity between their constitutional review systems and the lack of comparative studies on South American courts.