On April 3, 2025, the Nancy Administrative Court of Appeal annulled the authorizations granted by the prefect of Ardennes for the construction of the largest onshore wind farm planned in France, which planned a capacity of 226 MW, the installation of 63 wind turbines up to 200 meters high, and an electrical substation in seven communes of the department.

The court ruling responds to a lawsuit filed by the Collective for the Defense of the Mont des Quatre Faux Riverine Residents, who, along with other individuals, challenged the authorizations initially issued in 2017 and then amended in 2023. The ruling annuls both the original permit and the regularization attempt filed by the developer, Parc Éolien Mont des Quatre Faux.

Visual Impact: The Central Argument for the Annulment

One of the pillars of the ruling is the visual impact of the project. According to the court, the wind farm is located on a vast agricultural plateau with low vegetation density and no natural obstacles that mitigate the visibility of the turbines.

It notes that there are already numerous wind farms in the area surrounding the project, and that the technical indicators for visual saturation are greatly exceeded. In the case of the commune of Cauroy, for example, six wind turbines are located less than 2.5 km from the town center, achieving a horizon occupation index of 336°, a density index of 0.72 (when the threshold is 0.25), and a “visual breathing” angle of just 62°, well below the recommended minimum of 160°.

The ruling emphasizes that in all the affected communes—such as Machault, Mont-Saint-Remy, Dricourt, and Pauvres—wind density limits are significantly exceeded, with more than 150 wind turbines already installed within a 10-kilometer radius. “The disputed project, consisting of sixty-three additional wind turbines, significantly aggravates the enclosure of horizons,” the ruling concludes.

Technical and Environmental Deficiencies

The court also found serious flaws in the environmental procedure, even after the 2023 regularization attempt. It questions whether the updated impact assessment failed to take into account the evolution of the ecological context and the wind energy sector since 2015, when the first studies were conducted.

The visual models were deemed insufficient, as they did not adequately reflect the actual visibility of the wind farm in its surroundings and did not incorporate the newly constructed wind farms. Furthermore, the fauna assessments (birds and bats) did not conform to the updated conservation status of protected species, nor were derogation requests submitted pursuant to Articles L.411-1 et seq. of the Environmental Code.

The court also questions the lack of compensation measures for the destruction of habitats and protected species, as well as the absence of a new acoustic assessment adapted to the current context.

Arguments Rejected by the Developer and the State

The developer, Parc Éolien Mont des Quatre Faux, represented by Me Elfassi, argued that the new permit issued in October 2023 regularized the previously identified defects and requested that the project be maintained or, alternatively, that the ruling be suspended pending a new authorization. For its part, the Ministry of Ecological Transition maintained that the claims were unfounded, although it eventually agreed to suspend the permit pending a specific derogation for protected species.

Both arguments were rejected. The court concluded that “these effects do not appear to be able to be regularized without a very significant evolution of the project,” which would require a new impact assessment and a new public consultation process. Therefore, it has decided to annul both the previous ruling of the Châlons-en-Champagne administrative court (2020) and the two permits issued by the prefect: the initial one from 2017 and its modification from 2023.

Economic and administrative consequences

As a result of the decision, the State and the developer must each pay €1,500 to the Collective for the Defense of the Riverine People of Mont des Quatre Faux in legal fees. Furthermore, the project cannot move forward unless it is thoroughly redesigned and subject to a new environmental assessment in accordance with current regulations.

The ruling sets an important precedent for future wind power development in France, especially in regions where there are already high levels of deployment. While it does not question the principle of renewable energy development, it does establish that environmental and social limits must be respected in the host territories.