Intellectual Property Code
Section 73. Prior User. - 73.1. Notwithstanding Section 72 hereof, any prior user, who, in good faith was using the invention or has undertaken serious preparations to use the invention in his enterprise or business, before the filing date or priority date of the application on which a patent is granted, shall have the right to continue the use thereof as envisaged in such preparations within the territory where the patent produces its effect.
73.2. The right of the prior user may only be transferred or assigned together with his enterprise or business, or with that part of his enterprise or business in which the use or preparations for use have been made. (Sec. 40, R.A. No. 165a)