Which organization enforces regulations for the handling of controlled substances?

The Drug Enforcement Administration (DEA) is the organization responsible for enforcing regulations related to the handling of controlled substances in the United States. This includes the enforcement of laws governing the manufacture, distribution, and dispensing of drugs that have a potential for abuse or dependence. The DEA is a federal law enforcement agency under the Department of Justice and has the authority to regulate the classification of drugs into schedules based on their potential for abuse, as well as to inspect and oversee the activities of registrants such as pharmacies, hospitals, and practitioners who handle these substances.

The other organizations mentioned, while critical in their respective areas, do not directly enforce regulations regarding controlled substances. The World Health Organization focuses on international public health issues, the Centers for Disease Control and Prevention deals primarily with disease control and prevention with public health implications, and the National Institutes of Health conducts medical research and funding but does not enforce regulations concerning controlled substances. Thus, the DEA is uniquely positioned and mandated to oversee and enforce the laws pertaining to controlled substances in the United States.