Which agency is responsible for enforcing the Controlled Substances Act of 1970?

The Drug Enforcement Administration (DEA) is the agency responsible for enforcing the Controlled Substances Act of 1970. This act was established to regulate the manufacture and distribution of narcotics and other drugs that are deemed to have the potential for abuse. The DEA's role includes overseeing the legal trade of these substances, ensuring compliance with regulations, and taking appropriate action against any illegal activities related to controlled substances.

This focus on enforcement falls specifically under the jurisdiction of the DEA, distinguishing it from other agencies like the Food and Drug Administration (FDA), which primarily deals with drug approval and safety, the Occupational Safety and Health Administration (OSHA), which focuses on workplace safety, and the United States Department of Agriculture (USDA), which deals more with agricultural products and food safety. Thus, the DEA's specialized role in the regulation and enforcement related to controlled substances makes it the correct answer.