Despite the use of the term "national", the NEC is not a federal law. It is typically adopted by states and municipalities in an effort to standardize their enforcement of safe electrical practices. So the NEC Codes are adopted locally and enforcement of the NEC Code is a locally administered activity.
The NEC states the following as its purpose:
(A) Practical Safeguarding The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.
Notice that the word “practical” is used by the NEC. This means that means that a reasonable approach should be taken to ensuring safeguarding of persons and property from hazards that arise from the use of electricity must be made.
Let’s look at an important word before we continue:
ju·ris·dic·tion \ ˌju̇r-əs-ˈdik-shən \
1) The power, right, or authority to interpret and apply the law
2) The power or right to exercise authority: CONTROL
Jurisdiction descends from Latin jūrisdictiō, formed from jūris (from jūs "law") plus dictio "act of saying." Think of it as - who has the right to "say" what's "the law."
Next, let’s see what the NEC Code says about who has jurisdiction.
In Article 100 of the 2014 National Electrical Code (NEC), the term Authority Having Jurisdiction (AHJ) is defined as “An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.”
Authority Having Jurisdiction (AHJ)
The authority having jurisdiction (AHJ) is that person or office charged with enforcing the NEC Life Safety Code. In many states the AHJ is the state fire marshal who has local inspectors work on his/her behalf. In some cities, fire department fire prevention division personnel fulfill the role of AHJ; sometimes it is the building official. For some occupancies, there is more than one AHJ; each AHJ's approval must be secured. For example, the authorities having jurisdiction for a hospital might include: state fire marshal; building official; fire department fire prevention officer; state health care licensing agency; The Joint Commission; U.S. Department of Health and Human Services – Centers for Medicare and Medicaid Services (CMS); and the facility's insurance carrier.
But the important point here is that the AHJ is in charge, and that this person or group must be known. If you're unsure who the AHJ is, contact your state fire marshal.
The AHJ & NFL Football Referees - they are very similar systems (