Kernrechtsfrage
Whether the commune could enforce sewer connection costs by administrative contract rather than by formal decision.
Extrahierter Entscheid
In this setting, a contract was in principle possible, but only if validly concluded; here the written instrument was not a valid bilateral administrative contract.
Extrahierte Begründung
For off-zone sewer arrangements, contractual coordination is not excluded where the municipality is not itself obliged to provide the development. However, a valid administrative contract requires mutual agreement on all essential terms and written form; the signed paper mentioned only the owners' undertakings and did not state the municipality's reciprocal obligations.