Section 6. .

The secretary of state shall pass upon each petition, and if the secretary of state finds it insufficient, the secretary of state shall notify the “committee for the petitioners” and allow twenty days for correction. All decisions of the secretary of state in regard to any petition are subject to review by the supreme court. But if the sufficiency of the petition is being reviewed at the time the ballot is prepared, the secretary of state shall place the measure on the ballot and no subsequent decision shall invalidate the measure if it is at the election approved by a majority of the votes cast thereon. If proceedings are brought against any petition upon any ground, the burden of proof is upon the party attacking it and the proceedings must be filed with the supreme court no later than seventy-five days before the date of the statewide election at which the measure is to be voted upon.