North carolina constitution
Article V
Section 14

Notwithstanding the provisions of Section 2 of this Article, the General Assembly may enact general laws authorizing a county, city, or town that has defined a territorial area pursuant to this section to assess property within the territorial area at a minimum value if agreed to by the owner of the property, which agreed minimum value shall be binding on the current owner and any future owners as long as the defined territorial area is in effect.