That question was recently addressed in a judgement that was handed down by the French Supreme Court.

In the case, heard in the Cour de Cassation, a French national was hired as a sales executive by a US company based in France, a position he occupied for 8 years, when he was dismissed.

In court the manager challenged his senior executive status, as it granted fewer rights to compensation than would have been the case were he to have had merely managerial status.

As a result, he claimed damages in statute law for unpaid overtime, leave and violation of the rules on working hours. As part of the claim, he argued that the employment contract was not valid.

The working language of the company was English, and the employment contract had been drawn up in English, including the remuneration package.

The court of appeal rejected his claim, ruling that a contract in English was enforceable, and that his status as a senior executive precluded protection under French employment law.

Nevertheless, this decision was overturned in the Supreme Court. The court considered that "although the employee received one of the highest levels of remuneration in the company, it does not support the characterisation that, in the performance of his duties, the employee was entitled to make decisions in a largely autonomous manner, leading him to participate in the management of the company, therefore its decision has no legal basis on this point."

In addition, the court ruled that the document setting out the remuneration of the employee was invalid as it was not written in the French language.

Their ruling drew on Article 1321-6 of the Code de Travail, which states that any document containing obligations for the employee or knowledge necessary for the performance of his or her work must be drawn up in the French language.

The same Article separately states that this rule does not apply to contracts used outside of France by France based companies, or to foreign employees working in France (although in this case the employee was French).

Where the employee is a foreigner, the employee has the right to demand that a version of the contract in their native tongue should be provided. In the event of a dispute, both contracts are valid, and in the event of a discrepancy between the two contracts, the foreign language version takes precedence.