This new obligation was added to French Law no. 2016-41 of 26 January 2016 on the modernization of our public health system, in particular Article 19 .
Of course, the text also provided for the application and control procedures implementing this provision to be determined by decree of the French Council of State: the said decree has not been published to this day.
However, though cautious, Article 19 also stated this obligation would come into force ‘no later than January 1, 2017’.

As a result, the ARPP reminded that, in accordance with the law, and even in the absence of any decree, the indication ‘Photographie retouchée’ is now mandatory on the advertisements of the formats targeted, which, ‘in principle, should be as follows: displays and posters, online public communication, the press, advertising mailing sent to private individuals, and advertising prints intended for the general public.’
As a rule, meaning that, subject to the Council of State validation and the stance adopted by the European Commission, the content of the draft decree (submitted to the ARPP as part of its mandatory consultation), identifies as such the communication types and formats targeted by this obligation, referring to the ethical rules enacted by the ARPP for the presentation of the indication, and specifying the players’ responsibilities.

As a reminder, non-compliance with this new text may be punished by a €37,500 fine. The total sum of this fine may reach 30% of the expenses dedicated to advertising.

Source
• ARPP press release, 'Photographie retouchée' indication required in advertisements as from January 1, 2017 .