Pursuant to this established principle of federal legal preeminence, any state law that conflicts with federal law is generally considered preempted and therefore void. In addition to the 20 states and the District of Columbia that currently exempt qualified users of medicinal marijuana from penalties imposed under state law, Colorado and Washington in late 2012 became the first states to legalize, regulate, and tax small amounts of marijuana for personal (i.e., nonmedicinal) use by individuals over the age of 21. As a result, individuals who grow, possess, use, sell, transport, or distribute marijuana, even when done in a manner consistent with state law or pursuant to a state-issued license, are nonetheless in violation of the federal Controlled Substances Act (CSA) and remain subject to federal criminal prosecution or other consequences under federal law. Federal Preemption of State Law

The Colorado and Washington laws, which legalize, regulate, and tax an activity the federal government expressly prohibits, appear to be logically inconsistent with established federal policy and are therefore likely subject to a legal challenge under the constitutional doctrine of preemption. The Supremacy Clause, therefore, "elevates" the U.S. Constitution, federal statutes, federal regulations, and treaties above the laws of the states. As a result, where federal and state law are in conflict, the state law is generally preempted, leaving it void and without effect. Preemption Under the Controlled Substances Act

In Section 708 of the CSA (21 U.S.C. States remain free to pass laws relating to marijuana, or other controlled substances, so long as they do not create a "positive conflict" with federal law, such that the two laws "cannot consistently stand together." Application of Obstacle Preemption Principles to Washington and Colorado Legalization Measures

The extent to which a state law that legalizes, regulates, and taxes marijuana for recreational purposes may be preempted by the CSA is a novel and unresolved legal question. Are the Washington and Colorado Laws Preempted by International Law? The memorandum instructs federal prosecutors to prioritize their "limited investigative and prosecutorial resources to address the most significant [marijuana-related] threats" and identified the following eight activities as those that the federal government wants most to prevent: (1) distributing marijuana to children; (2) revenue from the sale of marijuana going to criminal enterprises, gangs, and cartels; (3) diverting marijuana from states that have legalized its possession to other states that prohibit it; (4) using state-authorized marijuana activity as a pretext for the trafficking of other illegal drugs; (5) using firearms or violent behavior in the cultivation and distribution of marijuana; (6) exacerbating adverse public health and safety consequences due to marijuana use, including driving while under the influence of marijuana; (7) growing marijuana on the nation's public lands; and (8) possessing or using marijuana on federal property. H.R. 499 , Ending Federal Marijuana Prohibition Act of 2013. H.R. 501 , Marijuana Tax Equity Act of 2013. H.R. 689 , States' Medical Marijuana Patient Protection Act. H.R. 710 , Truth in Trials Act. H.R. 784 , States' Medical Marijuana Property Rights Protection Act. H.R. 964 , Respect States' and Citizens' Rights Act of 2013. H.R. 1523 , Respect State Marijuana Laws Act of 2013. H.R. 1635 , National Commission on Federal Marijuana Policy Act of 2013. H.R. 2652 , Marijuana Businesses Access to Banking Act of 2013.
May a state authorize the use of marijuana for recreational purposes even if such use is forbidden by federal law? This novel and unresolved legal question has vexed judges, politicians, and legal scholars, and it has also generated considerable public debate among supporters and opponents of "legalizing" the recreational use of marijuana.
Under the federal Controlled Substances Act (CSA), the cultivation, distribution, and possession of marijuana are prohibited for any reason other than to engage in federally approved research. Yet 18 states and the District of Columbia currently exempt qualified users of medicinal marijuana from penalties imposed under state law. In addition, in November 2012, Colorado and Washington became the first states to legalize, regulate, and tax small amounts of marijuana for nonmedicinal (so-called "recreational") use by individuals over the age of 21. Thus, the current legal status of marijuana appears to be both contradictory and in a state of flux: as a matter of federal law, activities related to marijuana are generally prohibited and punishable by criminal penalties; whereas at the state level, certain marijuana usage is increasingly being permitted. Individuals and businesses engaging in marijuana-related activities that are authorized by state law nonetheless remain subject to federal criminal prosecution or other consequences under federal law.
The Colorado and Washington laws that legalize, regulate, and tax an activity the federal government expressly prohibits appear to be logically inconsistent with established federal policy toward marijuana, and are therefore potentially subject to a legal challenge under the constitutional doctrine of preemption. This doctrine generally prevents states from enacting laws that are inconsistent with federal law. Under the Supremacy Clause, state laws that conflict with federal law are generally preempted and therefore void and without effect. Yet Congress intended that the CSA would not displace all state laws associated with controlled substances, as it wanted to preserve a role for the states in regulating controlled substances. States thus remain free to pass laws relating to marijuana, or any other controlled substance, so long as they do not create a "positive conflict" with federal law, such that the two laws "cannot consistently stand together."
This report summarizes the Washington and Colorado marijuana legalization laws and evaluates whether, or the extent to which, they may be preempted by the CSA or by international agreements. It also describes and analyzes the U.S. Department of Justice's (DOJ's) response to these legalization initiatives as set forth in a memorandum sent to all federal prosecutors in late August 2013. The report then identifies certain noncriminal consequences that marijuana users may face under federal law. Finally, the report closes with a description of selected legislative proposals introduced in the 113th Congress relating to the treatment of marijuana under federal law, including H.R. 499 (Ending Federal Marijuana Prohibition Act of 2013); H.R. 501 (Marijuana Tax Equity Act of 2013); H.R. 689 (States' Medical Marijuana Patient Protection Act); H.R. 710 (Truth in Trials Act); H.R. 784 (States' Medical Marijuana Property Rights Protection Act); H.R. 964 (Respect States' and Citizens' Rights Act of 2013); H.R. 1523 (Respect State Marijuana Laws Act of 2013); H.R. 1635 (National Commission on Federal Marijuana Policy Act of 2013); and H.R. 2652 (Marijuana Businesses Access to Banking Act of 2013).