Local Government Code of 1991
Section 449. Manner of Creation. - A city may be created, divided, merged, abolished, or its boundary substantially altered, only by an Act of Congress, and subject to approval by a majority of the votes cast in a plebiscite to be conducted by the COMELEC in the local government unit or units directly affected. Except as may otherwise be provided in such Act. the plebiscite shall be held within one hundred twenty (120) days from the date of its effectivity.