2.3. The legislative history of the Convention coincides. A version of the Parol Evidence Rule was proposed by the Canadian delegate in Vienna.  The proposal was justified to limit admissible evidence in cases where the parties had decided to limit their agreement to the letter.  The Austrian representative indicated that his delegation was opposed to the amendment, insofar as it had to “limit the free assessment of the evidence” by the judge. To prevent a judge from verifying all the evidence, this would be contrary to a “basic principle of Austrian law”.  The representative of Japan also rejected the amendment, which he called “a re-establishment of the entry-into-force rule that prevailed in English-speaking common law countries.”  The only other nation that voted in favour of the proposal was Iraq. The amendment received little support and was rejected.  A merger clause obviously applies only to previous statements or agreements between the parties and does not exclude informal agreements subsequently concluded between them. However, the parties are free to extend an agreed form to future amendments (see Article 2.1.18). 1.2.1. The Parol Evidence Rule refers to the principles that the Common Law courts have developed to determine the role and weight of contractual writings.
The fundamental objective of these principles is to “preserve the integrity of written contracts by refusing the admission of oral [previous] or prior correspondence in contradiction with the written agreement.”  In order to enforce the intent of the letter, the judge may exclude extrinsic or parolian evidence, particularly statements made during negotiations. The Parol rule applies to the common law of contracts, including the right to sell ordinary legal orders.  In a very detailed and learned commentary, Thomas J.A. acknowledged that, on the basis of a strictly objective interpretation of the clause at issue, the conclusion could have been different, whereas it was only by taking into account the pre-contract negotiations between the parties and their statements of intent that it would have been clear that the parties had indeed given the importance of the Japanese seller to the clause at issue.  Although it indicates that the admission of such extrinsic evidence, article 8 of the ICSG, which is in force in New Zealand, and Articles 4.1 to 4.3 of the principles of UNIDROIT, which it considers to be a document which, in the very nature of a redefinition of world trade law [and] the extension of the principles of the United Nations Convention, is in agreement with Not to take a similar approach in this case and to stick to a literal or objective interpretation of the clause at issue.  Indeed, however desirable it was for the courts [page 23] in New Zealand to bring the law into line with the aforementioned international instruments, the Privy Council of London would not allow it, given that England has not yet adopted the ICSG and the English common law has traditionally opposed the admissibility of extrinsious evidence for the purposes of interpreting written agreements.  On appeal of an arbitration award in favour of the applicant, Gloster J. considered both whether the Lithuanian government had lifted sovereign immunity and whether it had accepted arbitration.  In considering the latter question, it examined the relevant rules of treaty interpretation in Articles 6.193 to 6.195 of the Lithuanian Civil Code and also cited in detail the commentary of a prominent Lithuanian scholar stating that these articles “repeat articles 4.1 to 4.6 of the principles of UNIDROIT”.
 Unlike English law, the aforementioned rules of treaty interpretation allow for a greater amount of material to interpret the importance of a contract.