a. Article 29 of the CISG deals with the requirements for the modification and termination of contracts. It further entrenches the principles of party autonomy, freedom of contract, and freedom from formalities contained in Article 11 of the CISG. These principles also form the foundation of the Principles of European Contract Law (PECL) as expressed in Articles 1:102, 2:101(2), and 2:106 and should therefore form the governing principles in the interpretation of any contract, as well as its modification or termination. Art 1:102 PECL, however, pertinently subjects the principle of freedom of contract to the principle of good faith and fair dealing, which may not be excluded.

b. The first object of Article 29 CISG is to reinforce the principle that any agreed modification or termination will be valid in whatever form it is made or contained. Its second object is to eliminate an important difference in approach between civil and common law, namely clearly establishing that no consideration is necessary for any amendment to be valid. However, it also entrenches the time-honored principle that, where parties have by agreement voluntarily restricted their ability to modify or terminate a contract by requiring formalities for such actions, that agreement will be valid and enforceable.

c. Article 2:106 PECL, which deals with written modification clauses, differs somewhat from Article 29 CISG in that it merely creates a presumption of invalidity where there is a clause requiring formalities for modification or termination.