Key legal question
Whether the ISOS inventory directly bound the owners and barred demolition
Extracted holding
ISOS is not directly owner-binding; it is only a federal concept to be considered in planning and balancing, unless cantonal law gives it direct effect.
Extracted reasoning
The court held that ISOS has no direct legal effect on private owners in Solothurn. It guides planning and federal tasks, but cannot create an immediate demolition ban for a private parcel not protected by valid cantonal or municipal instruments.