Facts

Co-owners C. and D. operate, through the company E. SA, an authorised vegetable greenhouse on plots located in an agricultural zone in Bernex (Geneva). The project to raise the height of this greenhouse, aimed at improving its ergonomics, was submitted to the Geneva Cantonal Department of Territory (DT) on 13 March 2019. After modifications, a third version of the project was submitted on 19 November 2020. The DT issued a construction permit on 14 January 2021, despite deviations from cantonal and federal regulations regarding building size and distances, subject to acceptance by the Geneva Cantonal Office of Agriculture and Nature (OCAN) regarding compliance with the zone.

Neighbours A. and B.A., owners of adjacent plots, contested this permit before the Geneva First-Instance Administrative Court (TAPI), which dismissed their appeal by judgment of 31 March 2022. The Geneva Administrative Chamber of the Court of Justice upheld this judgment by ruling of 30 August 2022. The Federal Supreme Court ultimately admitted the public law appeal and quashed the ruling of the Court of Justice.

Considerations

The Federal Supreme Court examined two main grounds raised by the appellants: 1) violation of their right to be heard and 2) violation of art. 16a para. 3 SPA regarding compliance of the project with the agricultural zone.

On the right to be heard: The Court dismissed this ground, finding that the Geneva Court of Justice had sufficiently reasoned its decision. The explanations provided by the lower court, particularly by relying on the department’s positions and detailing the reasoning, allowed the appellants to understand the grounds for the decision and to lodge an informed appeal. This reasoning met the requirements of art. 29 para. 2 Const. and federal case law (ATF 142 II 154 para. 4.2; ATF 137 II 266 para. 3.2).

On the merits: compliance of the project with the agricultural zone: The project to raise the height of the greenhouse, intended for soilless vegetable cultivation, could not be authorised either under internal development (art. 16a para. 2 SPA), as the area of soilless production exceeded the thresholds set by art. 37 SPO (5,000 m²), nor under the exceptions for existing structures (art. 24c SPA), as the project involved the demolition of the existing greenhouse and the construction of a new, taller one. Therefore, only art. 16a para. 3 SPA could potentially apply, provided that the project fell within a special agricultural zone designated through a zoning planning procedure.

The Federal Supreme Court reiterated that art. 16a para. 3 SPA requires a zoning planning procedure to…