In most countries marijuana is regulated by the Single Convention on Narcotic Drugs. In Japan marijuana use is illegal under the Marijuana Control Law. In USA, marijuana is also classified as a schedule I drug, which is the most stringent regulation category under federal law. On the other hand, California became the first state to legalize marijuana for medical uses in 1996. Since then, several other US states have approved marijuana for medical or recreational use. However, marijuana remains completely illegal in most states, while some allow only cannabidiol (CBD) extracted from marijuana for medical use. In June 2018, the US Food and Drug Administration approved Epidiolex, the first marijuana-derived drug, containing purified CBD, to treat certain rare childhood seizure syndromes. Therefore the situation surrounding control of marijuana in USA is complex. Recently, a definite trend toward reconsidering marijuana regulation has been seen around the world, which could have a major impact on marijuana policy in Japan. In this review, we investigated existing medical and recreational marijuana laws in various US states, with a focus on California, which approved recreational use in 2018. Here, we describe the current state of marijuana regulation in terms of both medical and recreational use. In addition, we discuss public safety issues associated with marijuana, including crime, traffic accidents, and emergency department visits from possible marijuana exposure, as well as generated tax revenues, from official marijuana-related reports in Colorado, which legalized marijuana use in 2012.