22 The VCLT does not introduce contract differentiation. Some articles of the VCLT refer to certain categories of contracts, such as Article 62, paragraph 2, point a), relating to contracts setting a limit and Article 5 on contracts constituting an instrument constituting an international organization. 27 The constituent instruments of international organisations are widely regarded as a particular category of contracts, in particular because of the particular rules of interpretation applicable to them, which involve both a more teleological approach in their interpretation and a particular attention to the practice developed by their institutions. An essential part of treaty drafting is that the signing of a treaty implies recognition, that the other party is a sovereign state and that the agreement, considered to be under international law, is applicable. Therefore, nations can be very cautious when it comes to qualifying a treaty agreement. In the United States, for example, interstate agreements are pacts and agreements between states and the federal government or between government authorities are statements of intent. 94 This principle derives from Article 31, paragraph 3, point c) of the VCLT and requires the interpretation of the treaty in light of “all relevant rules of international law applicable in relations between the parties.” This principle was one of the most neglected issues in treaty interpretation. However, it has become increasingly important in terms of the fragmentation of international law, its diversification and its expansion. 114 In multilateral treaties, it is now relatively common to insert so-called “conflictual” clauses, which must include explicit provisions to resolve problems related to a conflict between treaties (contracts, conflict clauses). They are also called “savings clauses” or “compatibility clauses.” Examples of these clauses are contained in the preamble to the Cartagena Protocol on the Prevention of Biotech Risks of the Convention on Biological Diversity [January 29, 2000, (2000) 39 ILM 1027], which states that “this protocol should not be construed as a change in the rights and obligations of a party under existing international agreements.” Article 311, paragraph 1 of the Convention on the Law of the Sea Article 73 The Vienna Convention on Diplomatic Relations ([entry into force on 18 April 1961] 500 UNTS 95); Article 137 Charter of the Organization of American States [signed on April 30, 1948, entered into force on December 13, 1951] 119 UNTS 3); and Article 8 of the North Atlantic Treaty [signed on April 4, 1949, which came into force on August 24, 1949] 34 UNTS 243).
The possibilities offered by these conflict clauses are quite complex and, in some possible situations, their impact is not entirely clear.