If a majority of the votes cast on the proposition favor its adoption, the initiated measure is enacted. If a majority of the votes cast on the proposition favor the rejection of an act referred, it is rejected. The lieutenant governor shall certify the election returns. An initiated law becomes effective ninety days after certification, is not subject to veto, and may not be repealed by the legislature within two years of its effective date. It may be amended at any time. An act rejected by referendum is void thirty days after certification. Additional procedures for the initiative and referendum may be prescribed by law. [Amended 1970]