On November 6, 1996, Republic Act 8223 was enacted to change Marikina from a Municipality to a City.
However, it needed the concurrence of the people of Marikina. Thus, on December 8, 1996, a plebiscite was held. Majority of those who voted was in favor and thus Marikina became a City.
You can download a copy of RA 8223 here