Section 8. If a majority of votes cast upon an initiated or a referred measure are affirmative, it shall be deemed enacted. An initiated or referred measure which is approved shall become law thirty days after the election, and a referred measure which is rejected shall be void immediately. If conflicting measures are approved, the one receiving the highest number of affirmative votes shall be law. A measure approved by the electors may not be repealed or amended by the legislative assembly for seven years from its effective date, except by a two-thirds vote of the members elected to each house.