That has nothing to do with the NEC.
The NEC has exceptions to the code all over the place. As an example, it allows for the use of conduit in residential homes (perhaps part of a city building code). but it describes the conduit types, wire size, wire type, temperature and even allowable conduit fill. It doesn't allow someone to use 18gauge lamp cord on a 15 amp circuit (as an example).
NFPA has adopted the NEC, as has UL, and all of the insurance companies.
So while local or state "authorities" may write in their own choices for wiring code(s), it is still under the descriptions covered by the NEC. No one can undermine or "lessen" the code (back to the 18 gauge example).