The principle of proportionality implies that the means used to achieve a given objective are limited to what is necessary and sufficient. A measure is considered to be compatible with the principle of proportionality if it pursues a legitimate aim and if the means employed are both necessary and as non-restrictive as possible; in other words, they must represent the minimum necessary to achieve that aim. This principle applies at all stages of the administrative procedure and prohibits the Competition Authority from imposing disproportionate burdens on undertakings.

With regard to sanctions, Article L. 464-2 of the Commercial Code requires that the fine be proportionate to the gravity of the practices, the extent of the damage caused to the economy, the situation of the undertaking and the recurrence of the practices. In order to ensure that the financial penalty is both dissuasive and proportionate, the Authority may further adjust, upwards or downwards, the basic amount thus defined in consideration of other objective elements specific to the situation of the undertaking or body in question.

According to the Conseil constitutionnel, administrative sanctions, particularly in competition matters, are, like criminal penalties, subject to the principle of proportionality. Consequently, their amount must “be in relation to the seriousness of the breaches committed and in relation to the benefits derived from the infringement“. The Conseil constitutionnel subsequently emphasized that “by seeking to punish an undertaking’s anticompetitive practices by means of a financial penalty, the maximum amount of which corresponds to 10% of the highest worldwide turnover excluding taxes realized during one of the financial years closed since the financial year preceding that in which the practices were implemented“, Article L. 464-2 “did not impose a penalty that is manifestly disproportionate in view, on the one hand, of the nature of the acts sanctioned and, on the other, of the fact that they have been and may still, even if  they have ceased, continue to provide the undertaking with illicit gains“.