N.C. Gen. Stat. § 128-36

Nothing in this Article shall have the effect of repealing any public-local or private act creating or authorizing the creation of any officers' or employees' retirement system in any county, city or town or prohibiting the enactment of any public-local or private act creating or authorizing the creation of any officers' or employees' retirement system in any county, city, or town. No payment on account of any benefit granted under the provisions of G.S. 128-27, subsections (a) to (d) inclusive, shall become effective or begin to accrue until the end of one year following the date the System is established nor shall any compulsory retirement be made during that period. The provisions of this Article shall apply only to those counties, cities or towns whose governing authorities voluntarily elect to be bound by same.