Section 125. Limitations upon Sanggunians. —

Any proposition or ordinance approved through the system of initiative and referendum as herein provided shall not be repealed, modified or amended by the sanggunian concerned within six (6) months from the date of the approval thereof, and may be amended, modified or repealed by the sanggunian within three (3) years thereafter by a vote of three-fourths (3/4) of all its members: Provided, That in case of barangays, the period shall be eighteen (18) months after the approval thereof.