NFPA 70, is a regionally adoptable standard for the nfpa 13 1999 pdf installation of electrical wiring and equipment in the United States. Despite the use of the term “national”, it is not a federal law. It is typically adopted by states and municipalities in an effort to standardize their enforcement of safe electrical practices.
In some cases, the NEC is amended, altered and may even be rejected in lieu of regional regulations as voted on by local governing bodies. The “authority having jurisdiction” inspects for compliance with these minimum standards. Work on the NEC is sponsored by the National Fire Protection Association.
First published in 1897, the NEC is updated and published every three years with the 2017 edition being the most current. Most states adopt the most recent edition within a couple of years of its publication. However, the NEC is the least amended model code, even with it setting minimum standards.
No court has faulted anyone for using the latest version of the NEC, even when the local code was not updated. Those who fail to adhere to well known best practices for safety have been held negligent.