Article L. 465-3-3 of the CMF makes index manipulation an offense, encompassing:

• the provision or transmission of false or misleading data or information used to calculate a benchmark index, or information likely to distort the price of a financial instrument or asset to which such an index is linked; or
• adopting any other behavior amounting to manipulation of how such an index is calculated.

An attempt to do the same also constitutes an offense.

A reference index is defined as any rate, index or number made available to the public or published, which is determined periodically or regularly by applying a formula or on the basis of the value of one or more underlying assets or prices, including estimates of actual or estimated prices, interest rates or other values, or survey data, and where reference to such an index determines the amount to be paid in respect of a financial instrument or the value of a financial instrument.

An offense is not committed in cases where the transaction or conduct is based on legitimate grounds, i.e. economically justified and not artificial or fictitious, and is in accordance with accepted market practices, within the meaning of Article 3(1)(9) of the MAR Regulation.