For some additonal perspective to this question, here is an excerpt from the State of Utah administrative rules governing building inspectors.
http://www.dopl.utah.gov/licensing/statutes_and_rules/R156-56.doc Note that as used in these rules "building inspector" is a generic term covering electrical inspectors, plumbing inspectors, etc.
Quote:
R156-56-502. Unprofessional Conduct - Building Inspectors.
"Unprofessional conduct" includes:
.
.
.
(10) approval of work which materially varies from approved documents that have been stamped by an architect, professional engineer or both unless authorized by the licensed architect, professional engineer or both;
End Quote
In the state of Utah an inspector is required to inspect to the approved plans. Other states or jurisdictions may have similar provisions.
