What action is illegal if a registrant knowingly uses access to controlled substances for personal benefit?

The action that is illegal when a registrant knowingly uses access to controlled substances for personal benefit is conversion. Conversion refers to the unauthorized use or appropriation of another's property for one's own use. In the context of controlled substances, this means that a registrant, who has legal access to these substances for specific purposes related to their professional duties, is misusing that access for personal gain. This misuse constitutes a serious violation of regulations governing controlled substances and undermines trust in the healthcare system.

Using controlled substances for personal benefit can pose significant risks not only to the individual misusing the substances but also to patients and the broader community. Such actions are considered both unethical and illegal, warranting strict penalties to deter this behavior. Recognizing conversion as the correct answer underscores the importance of accountability and proper conduct among registrants who have special access to sensitive materials.