Niboyet, J.-P. Keywords: Will | Autonomy | Law of contracts | Private international law | Mots clefs: Volonté | Autonomie | Droit des obligations | Droit international privé | ABSTRACT J.-P. Niboyet writes in the introduction to his course that without any exaggeration one can consider that the Theory of Party Autonomy is currently the most difficult of all private international law. Party Autonomy is commonly understood to mean the power of the parties to choose the competent law in matters of contracts, a law which is neve…