N.C. Gen. Stat. § 163-59
No person shall be entitled to vote or otherwise participate in the primary election of any political party unless that person complies with all of the following:
Notwithstanding the previous paragraph, any unaffiliated voter who is authorized under G.S. 163-119 may also vote in the primary if the voter is otherwise eligible to vote in that primary except for subdivisions (2) and (3) of the previous paragraph.
Any person who will become qualified by age to register and vote in the general election for which the primary is held, even though not so qualified by the date of the primary, shall be entitled to register for the primary and general election prior to the primary and then to vote in the primary after being registered. Such person may register not earlier than 60 days nor later than the last day for making application to register under G.S. 163-82.6(d) prior to the primary. In addition, persons who will become qualified by age to register and vote in the general election for which the primary is held, who do not register during the special period may register to vote after such period as if they were qualified on the basis of age, but until they are qualified by age to vote, they may vote only in primary elections.
N.C. Gen. Stat. § 163-59