Any lawful ordinance may be enacted by vote of the Town as follows:  A petition signed by not less than 15 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 selectmen shall have enacted the ordinance. The warning for the meeting shall include a summary of the text of the proposed ordinance, its effective date and penalty provision for violation thereof, and shall be posted and published as the law of this State requires for special meeting generally. The warning shall provide for a "yes" and "no" vote by ballot as to its enactment. Copies of the proposed ordinance shall be posted in its entirety in at least five locations in Town for at least 30 consecutive days to the date of said special Town meeting. In the discretion of the selectmen, the enactment of such ordinance may be proposed as an article in the warning for the next ensuing annual Town meeting, providing that such annual meeting shall be held within 120 days of the filing of such petition for enactment.