Key legal question
Whether the lease termination under Art. 257f CO was valid despite the premises being contractually leased for housing only.
Extracted holding
Yes. Regular use of residential premises for prostitution contradicted the agreed residential purpose and justified extraordinary termination after written protest.
Extracted reasoning
Art. 257f CO also applies when the tenant uses the property contrary to contractual purpose. Residential use excludes commercial exploitation; the landlord need not prove nuisance if the use itself violates the contract.