The provisions of RSA 31:94-a shall not take effect in any town, city or county unless adopted in the following manner:
I. In towns operating under the municipal budget law, by unanimous vote of the selectmen together with the approval of a 2/3 majority of the members of the budget committee, or by an article in the town warrant adopted by a majority of the legal voters of the town present and voting on such adoption;
II. In towns not operating under the municipal budget law, by an article in the town warrant, adopted by a majority of the legal voters of the town present and voting on such adoption;
III. In cities, by 2/3 vote of the city council;
IV. In counties, by majority vote of the members of the county convention present and voting.