Local Government Code of 1991
Section 9. Abolition of Local Government Units. - A local government unit may be abolished when its income, population, or land area has been irreversibly reduced to less than the minimum standards prescribed for its creation under Book III of this Code, as certified by the national agencies mentioned in Section 7 hereof to Congress or to the sangguniang concerned, as the case may be.
The law or ordinance abolishing a local government unit shall specify the province, city, municipality, or barangay with which the local government unit sought to be abolished will be incorporated or merged.