The building code requires the electrical inspector (or building inspector) to check the plans and specs of a job prior to issuing the permit. At the time of inspection, he will check the installation for code compliance AND compliance with the plans and specs. If there are any differences, then a good inspector will want the RFIs, and change order submittals to slip into the file as well.
On small jobs (residential) this is often waived, which is allowed by the building code.
The NEC is only a small part of the building code. Compliance with all parts is required.
It is true that only the codes adopted by your town/county/state will be law. Most places have adopted the ICC family of model codes, which reference the NEC for electrical.
Earl
