The IHR (2005) is an international agreement between 194 States Parties and the World Health Organization on surveillance, sunshine and response to all events that could pose a threat to international public health. The objective of the IHR (2005) is to prevent, protect, control and respond to a public health response to the spread of diseases internationally, in a manner adapted to public health risks, limited to them, avoiding unnecessary intervention in international transport and trade. (International Health Regulations, Article 2). For more information, please see THE LA fact sheets. The Tribunal found that treaties are subject to constitutional control and occupy the same hierarchical position as ordinary legislation (leis ordinrias, or « ordinary laws » in Portuguese). A recent ruling by Brazil`s Supreme Court in 2008 changed this situation somewhat by finding that treaties containing human rights provisions have a higher status than ordinary legislation, subject to the Constitution itself. In addition, the 45th Amendment to the Constitution provides for human rights treaties, approved by Congress as part of a specific procedure, the same hierarchical position as a constitutional amendment. The hierarchical position of the treaties with regard to national legislation is important for the debate on whether and how the former can cancel and vice versa. Brazil`s Federal Constitution stipulates that the power to enter into contracts is vested in the President of Brazil and that such contracts must be approved by the Brazilian Congress (Article 84, Clause VIII and Clause 49, Clause I). In practice, this has been interpreted to mean that the executive is free to negotiate and sign a treaty, but that its ratification by the President requires prior congressional approval. In addition, the Federal Supreme Court has ruled that after ratification and entry into force, a treaty must be enshrined in national law by a presidential decree issued in the Federal Register for it to be valid in Brazil and applicable by the Brazilian authorities. International contract law has been largely codified by the Vienna Convention on Treaty Law, which sets out the rules and procedures governing the establishment, modification and interpretation of contracts, as well as the resolution and resolution of disputes and alleged infringements.
 Treaties are considered to be one of the oldest manifestations of international relations as the main source of international law.  Once adopted, treaties and their amendments must follow the official legal procedures of the United Nations, as applied by the Legal Office, including signature, ratification and entry into force. A party may require that a contract be terminated, even without any explicit provision, if the circumstances have fundamentally changed. Such an amendment is sufficient when it is unforeseen, undermines the « essential basis » of a party`s agreement, radically alters the scope of commitments between the parties, and the commitments have yet to be fulfilled.