The law of treaties is set out in the 1969 Vienna Convention
One of the necessary aspects of the Vienna Convention is its scope. Article 1 of the Convention discusses the scope of the Convention stating that it applies to treaties that are concluded between States. Therefore, treaties that are completed between States and international businesses, or treaties conducted between multiple international businesses are outside of the Convention’s scope. The Convention is also limited to international agreements between States that are completed in written form and are governed by international law. Thus, any agreement that is not in written form, even if it is covered by international law, is not covered in the scope of the Convention.  According to Sinclair, he says that the Convention is ‘’retroactive, that is to say, it applies only to treaties which are concluded by States after the entry into force of the Convention with regard to such States.  ’’ Though the Convention is fairly detailed and broad, it is clear to see the limitations and strictness of the scope of the Convention.
An important Article of the Vienna Convention is Article 2(1)(d). This Article covers the definition of reservations which says:
‘’ “reservation" means a unilateral statement, however phrased or named, made by a State, when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State  ’’
Reservations are an importation part of the Vienna Convention as it allows States to apply treaties to their own specifications, and can apply outside of signatories to the Convention. Sinclair’s discussion on reservations says that ‘’a reservation is a declaration which is external to the text of a treaty,’’ and that at the time of its formulation, it is unilateral but it does not produce legal effects unless it is accepted by another state. 
Interpretations of a treaty are found in Articles 31 and 32. It is possible to interpret a treaty in various methods, specifically in these three methods: ‘’subjectively (intentions of the parties), objectively (textual), teleological (object and purpose).  ’’ However, the drafters on the Vienna Convention suggested a general rule of interpretation by stating the following: ‘’A treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose  ’’ which is found in Articles 31 and 32.
The concept of good faith is applied to the entire process of interpretations, ‘’including the examination of the text, the content and subsequent practice  ’’
In regards to the area of transnational law, it impossible to directly apply the Vienna Convention to transnational law as the Vienna Convention only applies to transactions occurred between States. However, as the Vienna Convention governs all treaties, it therefore governs a treaty that is vital to transnational law- the CISG. The CISG is unique in that it does not bind States, but it binds private parties within those States. The Vienna Convention and CISG work together to harmonize transnational law.
In order to understand how the Vienna Convention and the CISG work together to regulate transnational law, it is important to understand the CISG’s sphere of application, the structure and interpretation of rights and obligations within the CISG thus creating uniformity of the CISG and the Vienna Convention. Article 1(1)(a) of the CISG states that the Convention applies to contracts of sale of goods between the buyer and seller whose places of business are in different States when the States are Contracting States to the Convention  . This leads to the general applicability of the CISG. Compared to the Vienna Convention, the CISG is unique in that its sphere of application expands to parties within Contracting States. With this sphere of application, the CISG becomes a uniform law document for transnational sale of goods.
Though the CISG is broad in that it governs transactions carried out by businesses in different States, it still holds some limitations—such as those found in Article 4. The Article states that the Convention ‘’… governs only the formation of the contract of sale and the rights and obligations of the seller and buyer.  ’’ To critically evaluate Article 4, it is necessary to review Article 6 as they both present a clear understanding of the goal of those that have adopted the CISG. Article 6 states that ‘’ parties may exclude the application of this Convention or, subject to article 12, derogate from or vary the effect of any of its provisions.  ’’ Farnsworth’s critically evaluates the combination of Articles 4 and 6 by saying that, ‘’Articles six and four of the Convention create a tripartite hierarchy in which the Convention lies at the bottom, the agreement of the parties is in the middle, and the domestic law on validity rests on top.  ’’ These Articles allow for the CISG to apply to parties that are in different States, which may or may not be Contracting States, and most importantly, parties to a contract are able to exclude or vary the application of the CISG.
The CISG, along with the Vienna Convention allows for reservations. Article 95 of the CISG reads, “Any State may declare at the time of the deposit of its instrument of ratification, acceptance, approval or accession that it will not be bound by subparagraph (1) (b) of article 1 of this Convention.  " For example, Singapore, a Contracting party to the CISG, made a reservation to the CISG in hopes of limiting the scope of the application of the CISG so that ‘’under Singapore law, the CISG will apply to contracts of sale of goods between parties from different states only when both the states are Contracting States, and the CISG will not apply where one of the parties is not from a Contracting State.  ’’
With review of the CISG, is it clear to see that it is a vital and important legal document that regulates transnational law. The CISG is the only legal document that governs transnational law. However, without the Vienna Convention, the treaty of treaties, the CISG would not be applicable. Therefore, as the Vienna Convention regulates the CISG, it indirectly regulates transnational law.
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Attorney-General's Chambers- Singapore Government. ‘’Review of Article 95 Reservation Executive Summary’’ http://www.agc.gov.sg/publications/docs/CISG_Article_95_Report.pdf.
Farnsworth, E. Allan. ‘’Review of Standard Forms or Terms under the Vienna Convention’’
21 Cornell Int'l L.J. 447 (1988).
Sinclair, Ian. ‘’The Vienna Convention on the Law of Treaties: Second Edition." Manchester University Press. (Manchester, United Kingdom, 1984).
United Nations Commission on International Trade Law. ‘’United Nations Convention on Contracts for the International Sale of Goods.’’ http://www.uncitral.org/pdf/english/texts/sales/cisg/CISG.pdf
United Nations Treaty Collection. ‘’Vienna Convention on the Law of the Treaties.’’