I'm going to expand a bit on the above answers.
It is always legal to pay someone on a non-exempt basis. (note - not all non-exempt employees are paid hourly; not all exempt employees are paid on a salaried basis) The reverse is not true; not everyone can legally be paid by straight salary. It is the job duties, not the title, that determines who is and is not qualified for a straight salaried pay. If the duties do not meet the qualifications, it doesn't matter if you call that person a manager, a director, a vice president, a toaster, Gary, Bill Gates, or even God. If the job duties do not fit one or more of the legal definitions of an exempt employee, they MUST pay you as non-exempt.
However, if you do meet one or more of the legal definitions of exempt, the employer may STILL legally pay you as non-exempt.
NO state limits how many hours an employee may be required to work in a day. Only two states, neither of them NC, limits how many hours can be worked in a week/pay period. Approximately six or seven states require that an employee be given one day off out of every seven, but I do not recall that NC is one. There are a couple of industry specific exceptions to this (but they do not apply here), and many states limit how many hours a minor can be allowed to work. That represents the sum total of limitations that the states put on hours worked.
As a non-exempt employee working in NC, you must be paid at least (the higher of state or Federal, if different) minimum wage for every hour worked, and time and a half your regular rate of pay for any hours over 40 in a work week. If those standards are met, the law will assume that you have been paid correctly.
Neither Federal nor state law (in any state) puts any limits on what responsibilities the employer may hold you to.