Final answer:
The Controlled Substances Act established classifications of medications that had potential for abuse.
Step-by-step explanation:
The drug law that established classifications, known as schedules, of medications that had potential for abuse is the Controlled Substances Act (CSA). The CSA was passed by Congress in 1970 and declares marijuana as a dangerous drug. It is enforced by the Food and Drug Administration (FDA), which is empowered by the United States Congress to enforce the Federal Food, Drug, and Cosmetic Act (FD& Act).