From the Document: "Marijuana is listed as a Schedule I controlled substance under the Controlled Substances Act (CSA), and has been on Schedule I since the CSA was enacted in 1970 (P.L. 91-513). The Schedule I status of marijuana means that it is strictly regulated by federal authorities, regardless of state regulations and laws, and its growth, distribution, and possession (regardless of recreational or medicinal purposes) are prohibited under federal law aside from activities related to lawful research. Over the last several decades, states and territories have established a range of laws and policies regarding marijuana's medical and recreational use. Most states and territories have deviated from across-the-board prohibition of marijuana, and now have laws and policies allowing for some cultivation, sale, distribution, and possession of marijuana, while some states continue to prohibit any marijuana activity aside from lawful research. These developments have spurred a number of questions regarding potential implications for federal law enforcement activities as well as consequences for individuals who may be acting in accordance with state law but are in violation of federal drug laws and policies. There are many consequences of marijuana-related activity in the United States. This Insight focuses on the immigration consequences for noncitizens (referred to as 'aliens' in immigration law)."
CRS Insight, IN11503
Congressional Research Service: https://crsreports.congress.gov/