Any lawful ordinance may be enacted by vote of the Town as follows: A petition signed by not less than five percent of the registered voters shall be filed with the Town Clerk requesting enactment of the ordinance and accompanied by the text thereof. The selectmen shall call a special Town meeting to be held within 60 days of the date the petition is filed, unless prior to such meeting, the selectboard members shall have enacted the ordinance. The warning for the meeting shall include the text of the proposed ordinance and shall provide for a "yes" or "no" vote as to its enactment. The ordinance shall be adopted if at least 15 percent of the registered voters vote and a majority of that number vote for adoption. The ordinance shall take effect on the 30th day following adoption.