Controlled Substances Act (CSA): A Legal Overview for the 117th Congress [Updated February 5, 2021] [open pdf - 1MB]
From the Summary: "The Controlled Substances Act (CSA) establishes a unified legal framework to regulate certain drugs that are deemed to pose a risk of abuse and dependence. The CSA may apply to drugs that are medical or recreational, legally or illicitly distributed, but the statute does not apply to all drugs. Rather, it applies to specific substances and categories of substances that have been designated for control by Congress or through administrative proceedings. The CSA also applies to 'controlled substance analogues' that are intended to mimic the effects of controlled substances and to certain 'precursor chemicals' commonly used in the manufacturing of controlled substances."
CRS Report for Congress, R45948
Congressional Research Service: https://crsreports.congress.gov/