Question juridique clé
Whether the building permit was unlawful because it was issued before expropriation compensation or security for the derogation was determined.
Solution extraite
The cantonal authorities could not simply disregard the statutory security requirement; the lower court's justification was problematic, but the issue did not need definitive resolution for the outcome.
Motifs extraits
The security mechanism under cantonal planning law protects neighbors and may also influence the developer's conduct. No explicit exception for public authorities was shown, and the procedure was not so rigid as to justify ignoring it as mere formalism.