The judgment of the Supreme Court of Colombia, rendered upon the petition by a citizen to declare Law 20 of 1974, approving the concordat between the Holy See and Colombia, to be unconstitutional, deals with one of the most controversial aspects of the interface between international law and constitutional law under many modern constitutions. In most contemporary constitutional systems, the conclusion of international agreements requires parliamentary participation. In the United States only one house—the Senate—must give its advice and consent, but in the majority of states with bicameral systems, including Colombia, the approval must be given by both houses, usually in the form of a statute, the so-called ratification law. According to Article 120, subsection 20, of the Constitution of Colombia,
it is the task of the President, as head of the state and highest administrative authority, to conduct the diplomatic and commercial relations with the other nations and entities under international law … and to conclude with other nations and entities under international law treaties and conventions, which are to be subject to approval by Congress.
