The second power reserved is the referendum which may be invoked, by petition, against any act or part of an act of the Legislature, except those making appropriations for the expense of the state government or a state institution existing at the time of the passage of such act. Petitions invoking the referendum shall be signed by not less than five percent of the registered voters of the state, distributed as required for initiative petitions, and filed in the office of the Secretary of State within ninety days after the Legislature at which the act sought to be referred was passed shall have adjourned sine die or for more than ninety days. Each such petition shall set out the title of the act against which the referendum is invoked and, in addition thereto, when only a portion of the act is sought to be referred, the number of the section or sections or portion of sections of the act designating such portion. No more than one act or portion of an act of the Legislature shall be the subject of each referendum petition. When the referendum is thus invoked, the Secretary of State shall refer the same to the electors for approval or rejection at the first general election to be held not less than thirty days after the filing of such petition.
When the referendum is invoked as to any act or part of act, other than emergency acts or those for the immediate preservation of the public peace, health, or safety, by petition signed by not less than ten percent of the registered voters of the state distributed as aforesaid, it shall suspend the taking effect of such act or part of act until the same has been approved by the electors of the state.