What is the implication of NEC's "first rule"?

The implication of the NEC's "first rule" is that if a practice or installation method is not specifically allowed by the code, then it is considered prohibited. This foundational principle establishes a framework that enhances safety and standardization in electrical installations. The idea is to ensure that all electrical work adheres to recognized safety guidelines, preventing potentially hazardous practices that could lead to accidents, damage, or unsafe conditions.

This understanding helps electricians and contractors to operate within safe and legal boundaries, avoiding any assumptions about what might be acceptable if not expressly stated. Therefore, conducting an installation or using specific materials or methods that are not detailed in the code would be unsafe and potentially illegal, reaffirming the importance of compliance with the NEC standards.