1. According to article 6 of the Convention, the parties may exclude the Convention's application (totally or partially) or derogate from its provisions. Therefore, even if the Convention is otherwise applicable, one must nevertheless determine whether the parties have excluded it or derogated from its provisions in order to conclude that the Convention applies in a particular case.[4]
2. By allowing the parties to exclude the Convention and derogate from its provisions, the drafters affirmed the principle according to which the primary source of the rules governing international sales contracts is party autonomy.[5] In doing so, the drafters clearly acknowledged the Convention's non-mandatory nature [6] and the central role that party autonomy plays in international commerce and, in particular, in international sales.[7]
Derogation
3. Article 6 makes a distinction between the exclusion of the application of the Convention and the derogation from some of its provisions. Whereas the former does not encounter any limitations, the latter does. Where one of the parties to the contract for the international sale of goods has its place of business in a State that has made a reservation under article 96,[8] the parties may not derogate from or vary the effect of article 12. In those cases, any provision "that allows a contract of sale or its modification or termination by agreement or any offer, acceptance or other indication of intention to be made in any form other than in writing does not apply" (art. 12). All other provisions may be derogated from.[9]
4. Although the Convention does not expressly mention it, there are other provisions that the parties cannot derogate from, more specifically, the public international law provisions (i.e. arts. 89-101). This is due to the fact that those provisions address issues relevant to contracting States rather than private parties. It should be noted that this issue has not yet been addressed by case law.