1987 Constitution of the Philippines
Section 2. Amendments to this Constitution may likewise be directly proposed by the people through initiative upon a petition of at least twelve per centum of the total number of registered voters, of which every legislative district must be represented by at least three per centum of the registered voters therein. No amendment under this section shall be authorized within five years following the ratification of this Constitution nor oftener than once every five years thereafter.
The Congress shall provide for the implementation of the exercise of this right.