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 UNIDROIT Principles of International Commercial Contracts as expressed in Articles 1.1, 1.5, and 2.18 and should therefore form the governing principles in the interpretation of any contract as well as its modification or termination.

b. Article 2.18 of the UNIDROIT Principles in itself sheds little light on the interpretation or augmentation of Article 29 of the CISG as both Articles are formulated in almost exactly the same words, with one insignificant exception. Where Article 2.18 of the UNIDROIT Principles deals with the abuse of the written modification clause, it refers to the prohibition to rely on such clause to the extent that the other party has “acted in reliance” on that conduct. The CISG merely refers to the extent that the other party has “relied on that conduct.” It is submitted that nothing turns on this divergence as reliance in itself implies some action or failure to act on the part of that party.

c. In interpreting the scope of Article 2.18 of the UNIDROIT Principles, regard should also be had to the provisions of Article 3.2, which deals with freedom of form and formalities.