The federal Controlled Substances Act (CSA) outlaws the possession, cultivation, or distribution of marijuana except for authorised research. Twenty states have regulatory schemes that allow possession, cultivation, or distribution of marijuana for medicinal purposes. Two have revenue regimes that allow possession, cultivation, or sale generally. The U.S. Constitution's Supremacy Clause preempts any state law that conflicts with federal law. Although there is some division, the majority of state courts have concluded that the federal-state marijuana law conflict does not require preemption of state medical marijuana laws. The legal consequences of a CSA violation, however, remain in place. Nevertheless, current federal criminal enforcement guidelines counsel confining investigations and prosecutions to the most egregious affront to federal interests. This book analyses some legal issues related to marijuana and provides some proposals to resolve the issues. It also discusses federal tax proposals for marijuana.