Which statement best describes Mandatory Rules in the NEC?

• A. They require action or prohibition as indicated by 'shall' or 'shall not'
• B. They are optional guidelines
• C. They are recommendations only
• D. They are defined by the AHJ

Answer: (A)

In the NEC, the binding requirements are signaled by the words “shall” or “shall not.” When a rule uses this language, it means an action must be taken or prohibited—it's a mandatory rule that must be followed for code compliance. That’s why the best description is that these statements require action or prohibition as indicated by “shall” or “shall not.”

This isn’t about optional guidelines or mere recommendations, which would use softer terms like “should,” “may,” or “recommended.” The Authority Having Jurisdiction enforces the code and can interpret or modify local adoption, but the mandatory nature comes from the code language itself, not from the AHJ creating the rule.