Who is responsible for checking the legality of initiatives?

Constitution (2017)

Section 128. The House of Representatives and the Senate have the power to enact rules of procedure governing the election and performance of duties of the President, Vice-Presidents, matters or activities which are within the duties and powers of each standing committee, performance and quorum of committees, sittings, submission and consideration of organic law bills and bills, submission of motions, consultation, debate, passing of a resolution, recording and disclosure of the passing of a resolution, interpellation, general debate, observation of the rules and orders and other relevant matters, as well as the power to enact rules of procedure regarding the code of ethics of members and committee members and other matters for the implementation of the Constitution.

The rules of procedure under paragraph one in the part concerning the appointment of an ad hoc committee for the consideration of bills the substance of which is decided by the President of the House of Representatives to concern with children, youths, women, the elderly, the disabled or handicapped, shall stipulate that such ad hoc committee consists of the said types of persons or representatives from private organisations concerned directly with the respective types of persons, of at least one-third of the total number of the ad hoc committee members, and in the part concerning the consideration of bills introduced by a petition of persons having the right to vote, shall stipulate that such ad hoc committee consists of representatives of the persons having the right to vote who sign a joint petition to introduce such bill, of at least one-third of the total number of the ad hoc committee members.