The Controlled Substances Act (CSA) is a federal law in the United States that regulates the manufacture, distribution, and use of certain drugs and substances. It classifies these substances into five schedules based on their potential for abuse, medical use, and safety. Schedule I substances, like heroin and LSD, have the highest potential for abuse and no accepted medical use, while Schedule V substances, such as cough preparations with low doses of codeine, have the lowest potential for abuse. The CSA aims to prevent drug abuse and protect public health by controlling access to these substances. It establishes a framework for the legal handling of drugs, requiring registration for manufacturers and distributors, as well as prescriptions for patients. The law is enforced by agencies like the Drug Enforcement Administration (DEA), which monitors compliance and investigates violations.