That would be the "Forbidden by contract". If Bob has a lease with Ann that forbids short term rental of a room, then Ann can persue legal action against bob i

That would be the "Forbidden by contract". If Bob has a lease with Ann that forbids short term rental of a room, then Ann can persue legal action against bob including damages and eviction Only Ann has the right to do this however, not AirBnB, not the neighbors, no one else besides Ann. AirBnB has no obligation to know about, enforce, or ask about any contract or agreements Bob may have with Ann. I will add also that if Ann contacts AirBnB as the owner of the property AirBnb has an obligation to remove the listing. Often however I see less property owners complaining about AirBnB and more neighbors who simply assume the Tenant does not have permission to sublet (which I would not really call AirBnB as sublet either but...).