The content of bilateral investment treaties is to the great extend standardized. One of the provisions that are regularly included into the bilateral investment treaties concerns "application of other rules". Although, the provision itself is raised by investors or host states in investment arbitration sparsely, it has been raised by the investors to overcome negative decisions on more standard provisions under the bilateral investment treaties. The aim of this paper is to analyse the provision on application of other rules and determined whether it may be employed to grant additional rights to the foreign investors under the bilateral investment treaties.