A contract shall be governed by the law chosen by the parties. The choice must be express or demonstrated with reasonable certainty by the terms of the contract or the circumstances of the case. By their choice the parties can select the law applicable to the whole or a part only of the contract.

The parties may at any time agree to subject the contract to a law other than that which previously governed it, whether as a result of an earlier choice under this Article or of other provisions of this Convention. Any variation by the parties of the law to be applied made after the conclusion of the contract shall not prejudice its formal validity under Article 9 or adversely affect the rights of third parties.

The fact that the parties have chosen a foreign law, whether or not accompanied by the choice of a foreign tribunal, shall not, where all the other elements relevant to the situation at the time of the choice are connected with one country only, prejudice the application of rules of the law of that country which cannot be derogated from by contract, hereinafter called “mandatory rules”.

The existence and validity of the consent of the parties as to the choice of the applicable law shall be determined in accordance with the provisions of Articles 8, 9 and 11.