La. Stat. tit. 33 § 4780.5
Regulations, restrictions, and boundaries established pursuant to this Subpart may, from time to time, be amended, supplemented, changed, modified, or repealed. However, in the event of a protest against a change duly signed and acknowledged by the owners of twenty percent or more, either of the areas of land, exclusive of streets and alleys, included in a proposed change or within an area determined by lines drawn parallel to and two hundred feet distant from the boundaries of the district proposed to be changed, the amendment shall not become effective except by the favorable vote of a majority of the members of the governing authority of St. Helena Parish who are present and voting. The provisions of R.S. 33:4780.4 relative to public hearing and official notice shall apply equally to all changes or amendments; however, no ordinance shall require a procedure or criteria for amendment any greater than that initially used in establishing such regulations, restrictions, or penalties.
La. R.S. § 33:4780.5