19 There are groups of agreements which, although concluded under international law, fall under national law, such as the acquisition of property by a state. Another group is that of agreements between states and a foreign individual, physical or legal (contracts between foreign states and individuals), such as Z.B concession contracts, the character of which is not entirely clear. One view is that such an agreement is concluded in international law if the parties so, and that the prerequisite for an international treaty is the existence of at least two parties subject to international law. In 1952, the ICJ maintained that a concession contract between the United Kingdom and the Iranian oil company was a private contract (112). The distinctions are mainly related to their method of authorisation. Contracts must be advised and approved by two-thirds of the senators present, but executive agreements alone can be executed by the President. Some contracts give the president the power to fill gaps through executive agreements rather than additional contracts or protocols. Finally, agreements between Congress and the executive branch require the approval of the House of Representatives and the Senate before or after the president signs the treaty. 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. First, the conflict clause can be included either in a previous contract, in a subsequent contract, or in both.
Moreover, regardless of the contract in which the clause is included, it may either (a) aim to ensure the priority of the future contract (in this case, it cannot, in fact, express only the general rule of the lex posterior; b) obtain the effect of the previous treaty; or (c) if they are effectively incorporated into the previous treaty in order to prevent States Parties from concluding agreements in the future contrary to the previous treaty. It must be said that not all potential conflicts can be resolved by the application of relevant principles if mutually exclusive commitments arise. Before 1871, the U.S. government regularly entered into contracts with Indians, but the Indians Appropriation Act of March 3, 1871 (Chapter 120, 16 Stat. 563) had a horseman (25 US. C No. 71), which effectively ended the drafting of presidential treaties by declaring that no Indian nation or Indian tribe can be recognized as a nation, tribe or independent power with which the United States can enter into contractual contracts.