Marijuana is the most commonly used illicit drug in the United States. It is a psychoactive drug that generally consists of leaves and flowers of the cannabis sativa plant. Its history dates back thousands of years, but in the United States, it became popular as a recreational drug in the early 20 th century. The THC content of marijuana is dependent on both the variety of the cannabis plant and the part used. Under federal law, cannabis and its derivatives are classified as Schedule I controlled substances—thus prohibiting their possession, cultivation, or distribution—under the Controlled Substances Act (CSA), regardless of its THC content, unless specifically exempted or listed in another schedule (see " Controlled Substances Act "). The percentage of the population 12 and older currently using (past month use of) marijuana has generally increased over the last several years—from 6.9% in 2010 to 8.3% in 2015. The rate of past-month marijuana use among youth (aged 12-17), however, has remained relatively unchanged over this period (7.0%). Youth also generally perceive that obtaining marijuana—if they desire it—is relatively easy. Indeed, marijuana is available throughout the United States; 34% of state and local law enforcement agencies that were surveyed by the Drug Enforcement Administration (DEA) reported an increase in availability over the last year, and 62% reported that availability had remained the same. This report provides a background on federal marijuana policy and an overview of state trends with respect to marijuana decriminalization and legalization—for both medical and recreational uses. It then analyzes relevant issues for federal law enforcement and the implications of state marijuana legalization. The report also outlines a number of related policy questions that Congress may confront, including legalization in the District of Columbia, financial services for marijuana businesses, the medical nature of marijuana, oversight of federal law enforcement, and evaluation of marijuana as a Schedule I drug. Marijuana is currently listed as a Schedule I controlled substance under the CSA. This indicates that the federal government has determined that (A) The drug or other substance has a high potential for abuse. (B) The drug or other substance has no currently accepted medical use in treatment in the United States. (C) There is a lack of accepted safety for use of the drug or other substance under medical supervision. U.S. federal drug control policies—specifically those positions relating to marijuana—continue to generate debates among policymakers, law enforcement officials, scholars, and the public. Even before the federal government's move in 1970 to criminalize the manufacture, distribution, dispensation, and possession of marijuana, there were significant discussions over marijuana's place in American society. Changes in state and local marijuana laws are coupled with a general shift in public attitudes toward the substance. In 1969, 12% of the surveyed population supported legalizing marijuana; today, 60% of surveyed adults feel that marijuana should be legalized. Support for legalization has more than doubled over the last 20 years. In addition, nearly 60% of respondents indicate that the federal government should not enforce federal marijuana prohibition laws in those states that allow for its use. As mentioned, marijuana's placement on Schedule I of the CSA means that it has no currently accepted medical use according to the federal government. Under federal law, marketing a drug as medicine requires approval from the Food and Drug Administration (FDA). While most states have laws allowing for medicinal use of marijuana, the FDA has not approved marijuana, any drug containing marijuana, or any drug containing a plant-derived chemical constituent of marijuana for medicinal use. The FDA has, however, approved two drugs containing synthetic THC. In addition, drugs containing plant-derived THC and/or cannabidiol (CBD, a nonpsychoactive chemical component of marijuana) are in the drug development and approval process. See Appendix A for further discussion of these drugs. Individuals use marijuana to treat medical issues such as lack of appetite, nausea, chronic pain, spasticity, anxiety, and other maladies; however, the efficacy of this treatment is unclear from available scientific evidence. While some individuals report (both anecdotally and in scientific studies) benefits and alleviation of symptoms from use of marijuana, reports are inconsistent. Some have argued that the scientific field has been unable to robustly determine the medicinal value and merits of marijuana due to regulatory restrictions on quality, quantity, and use of marijuana in scientific research. Recent evaluations conducted separately by the FDA and the National Academies of Sciences, Engineering, and Medicine (the National Academies) illustrate the challenge of meeting the required standard of evidence for demonstrating effective medical use. While taking different approaches to their evaluations, both the FDA and the National Academies have found that the current evidence base falls short. According to the FDA, "no published studies conducted with marijuana meet the criteria of an adequate and well-controlled efficacy study," and "the criteria for adequate safety studies [have] also not been met." According to the National Academies, "conclusive evidence regarding the short- and long-term health effects (harms and benefits) of cannabis use remains elusive." These studies are discussed in more detail in Appendix A . Individuals who seek to conduct research on any controlled substance must do so in accordance with the CSA and other federal laws. For all controlled substances, individuals must obtain a registration issued by the Attorney General, as delegated to the DEA in accordance with associated rules and regulations issued by the Attorney General. Also, DEA regulations require all registrants to comply with strict storage requirements for controlled substances. Some have argued that federal regulation of marijuana research unnecessarily impedes the clinical trials that are required for FDA approval, and the Obama Administration simplified some small steps within the larger process. In recent years, the federal government has attempted to make marijuana research easier. In June 2015, HHS eliminated one step in obtaining research-grade marijuana for research that is not funded by the National Institutes of Health. In December 2015, the DEA announced a waiver to make it easier for researchers conducting clinical trials with CBD to modify their research protocols and obtain more CBD than was initially approved. In August 2016, the DEA announced a new policy intended to increase the number of approved sources of research-grade marijuana. Prior to the August 2016 change, some contended that marijuana provided to researchers was "both qualitatively and quantitatively inadequate." The DEA's recent policy change may appease those researchers seeking better quality and quantity of marijuana. For broader discussion of this issue, see Appendix A . While the federal government maintains marijuana's current placement as a Schedule I controlled substance, states have established a range of laws and policies regarding its medical and recreational use. These developments have spurred a number of questions regarding potential implications for federal drug enforcement activities and for the nation's drug policies as a whole. In 1970, the CSA placed the control of marijuana under federal jurisdiction regardless of state regulations and laws, and its status has remained unchanged under federal law for nearly 50 years. For more background on federal marijuana policy and the history of how marijuana came to be illegal in the United States, see Appendix B . There has been mounting public pressure for the DEA to reevaluate marijuana as a Schedule I controlled substance. Over the years, several entities have submitted petitions to reschedule marijuana. In August 2016, after a five-year evaluation process done in conjunction with the Food and Drug Administration (FDA), the DEA rejected two petitions submitted by two state governors and a New Mexico health provider, respectively, to move marijuana to a less-restrictive schedule under the CSA. Consistent with past practice, the rejections were based on a conclusion by both the FDA and DEA that marijuana continues to meet the criteria for inclusion on Schedule I—namely that it has a high potential for abuse, has no currently accepted medical use, and lacks an accepted level of safety for use under medical supervision. It is important to note that both Congress and the Administration have the power to alter marijuana's status as a Schedule I substance. Congress could amend the CSA to move marijuana to a lower schedule or remove it entirely from control. The Administration could also make such changes on its own, though it is bound by the CSA to evaluate a substance prior to altering its scheduling status. Over the past few decades, most states have deviated from an across-the-board prohibition of marijuana, and as of March 2017, nearly 90% of the states, as well as Puerto Rico and the District of Columbia, allowed for the medical use of marijuana in some capacity. Also, eight states and the District of Columbia now allow for the recreational use of marijuana. It is now more so the rule than the exception that states have laws and policies allowing for some manufacturing, sale, distribution, and possession of marijuana—all of which are contrary to the CSA, except for the purposes of sanctioned research. Evolving state-level positions on marijuana include decriminalization initiatives, legal exceptions for medical use, and legalization of certain quantities for recreational use. See Figure 2 at the end of this section for the various marijuana policies of states. Decriminalization and legalization initiatives in the states reflect growing public support for the legalization of marijuana. As mentioned, just prior to passage of the CSA in 1970, 12% of surveyed individuals aged 18 and older felt that marijuana should be made legal. In 2016, more than half (60%) of surveyed U.S. adults expressed that marijuana should be legalized. Marijuana decriminalization differs markedly from legalization . A state decriminalizes conduct by removing the accompanying criminal penalties; however, civil penalties remain. If, for instance, a state decriminalizes the possession of marijuana in small amounts, possession of it still violates state law, but possession of quantities within the specified small amount is considered a civil offense and subject to a civil penalty, not criminal prosecution. By decriminalizing possession of marijuana in small amounts, states are not legalizing its possession. In addition, as these initiatives generally relate to the possession (rather than the manufacture or distribution) of small amounts of marijuana, decriminalization initiatives do not impede federal law enforcement's priority of targeting high-level drug offenders, or so-called "big fish," rather than individual users. Decriminalization initiatives by the states do not appear to be at odds with the CSA because both maintain that possessing marijuana is in violation of the law. For example, individuals in possession of small amounts of marijuana in Nebraska—a state that has decriminalized possession of small amounts—are in violation of both the CSA and Nebraska state law. The difference lies in the associated penalties for these federal and state violations. Under the CSA, a person convicted of simple possession (first offense) of marijuana may be punished with up to one year imprisonment and/or fined not more than $1,000. Under Nebraska state law, a person in possession (first offense) of an ounce or less of marijuana is subject to a civil penalty of not more than $300. In recent years, several states have decriminalized the possession of small amounts of marijuana; however, some of these states continue to treat possession of small amounts of marijuana as a criminal offense under specific circumstances. In New York, for example, the possession of small amounts of marijuana is still considered a crime when it is "open to public view." In 2015, just over 21,000 individuals in New York were arrested for criminal possession of marijuana in the fifth degree, a misdemeanor. Several cities have officially or unofficially decriminalized marijuana possession regardless of what has occurred at the state level. In November 2014, New York City (NYC) Mayor de Blasio and NYC Police Commissioner Bratton announced a change in marijuana enforcement policy; individuals found to be in possession of marijuana (25 grams or less) may be eligible to receive a summons instead of being arrested. The New York City Police Department (NYPD) issues so-called "pot tickets" for those in possession of 25 grams or less. In 2016, however, preliminary data indicated that marijuana possession arrests were increasing in NYC compared to 2015—this increase could be the result of changes in NYPD arrest policies; this remains unclear. Just as there are disparities in state and federal laws and policies, some cities' decriminalization initiatives run contrary to the laws and policies of the states. In Pennsylvania, the state government has not decriminalized marijuana possession, but Pittsburgh, Philadelphia, State College, and Harrisburg have all decriminalized possession in some form. In 2016, Harrisburg's city council unanimously voted to make possession of 30 grams or less of marijuana punishable by a $75 fine and public use punishable by a $150 fine. In 1996, California became the first state to amend its drug laws to allow for the medicinal use of marijuana. As of March 2017, over half of the states, the District of Columbia, Puerto Rico, and Guam have comprehensive policies allowing for the medicinal use of marijuana. Seventeen additional states allow for so-called "limited access medical marijuana," which refers to cannabis with low THC content or CBD oil. As noted, the CSA does not distinguish between the medical and recreational use of marijuana. Under the CSA, marijuana has "no currently accepted medical use in treatment in the United States," and states' allowance of its use for medical purposes is at odds with the federal position. Federal law enforcement has investigated, arrested, and prosecuted individuals for medical marijuana-related offenses regardless of whether they are in compliance with state law; however, federal law enforcement emphasizes the investigation and prosecution of growers and dispensers over individual users of medical marijuana. Federal enforcement priorities are discussed further in " Federal Response to State Divergence ." In contrast to marijuana decriminalization initiatives wherein civil penalties remain for violations involving marijuana possession, marijuana legalization measures remove all state-imposed penalties for specified activities involving marijuana. Until 2012, the recreational use of marijuana had not been legal in any U.S. state since prior to the passage of the CSA in 1970. In November 2012, citizens of Colorado and Washington voted to legalize, regulate, and tax small amounts of marijuana for recreational use. In November 2014, legalization initiatives also passed in Alaska, Oregon, and the District of Columbia (DC), further expanding the disparities between federal and state marijuana laws. Later, in November 2016, recreational legalization initiatives passed in Massachusetts, California, Maine, and Nevada. These recreational legalization initiatives all legalized the possession of specific quantities of marijuana by individuals aged 21 and over and (with the exception of DC) set up state-administered regulatory schemes for the sale of marijuana; however, there are variations among the initiatives. For example, Colorado, Alaska, Oregon, Massachusetts, Nevada, Maine, California, and DC allow for individuals to grow their own marijuana plants while Washington does not. These legalization initiatives also specify that many actions involving marijuana remain crimes. For example, in Washington, as well as other states, the operation of a motor vehicle while under the influence of marijuana remains a crime. In some states such as Colorado, individuals over the age of 21 may grow small amounts of marijuana for personal use, but marijuana may not be consumed "openly and publicly or in a manner that endangers others." In an example of city-level initiatives breaking from state-level policies, in November 2016, the city of Denver voted to allow designated areas where public consumption of marijuana would be allowed. Figure 2 highlights the status of marijuana laws by state. Rather than targeting individuals for drug use and possession, federal law enforcement has generally focused its counterdrug efforts on criminal networks involved in the drug trade. Notably, federal policing efforts on marijuana enforcement appear consistent with this position. Federal marijuana enforcement efforts have largely been focused on traffickers and distributors of illicit drugs, rather than the low-level users; rather, arrests for marijuana possession offenses are largely made by state and local police. President Obama once noted that "[it] would not make sense from a prioritization point of view for us to focus on recreational drug users in a state that has already said that under state law that's legal." While it is not yet clear how the Trump Administration will proceed with drug enforcement priorities, the White House press secretary indicated there may be increased enforcement against recreational marijuana, and stated that there is a "big difference" between medical and recreational marijuana. After some states began to legalize the medical use of marijuana, the Department of Justice (DOJ) reaffirmed that marijuana growth, possession, and trafficking remain crimes under federal law irrespective of how individual states may change their laws and positions on marijuana. DOJ has clarified federal marijuana policy through several memos providing direction for U.S. Attorneys in states that allow the medical use of marijuana. In the so-called "Ogden Memo" of 2009, former Deputy Attorney General David Ogden reiterated that combating major drug traffickers remains a central priority and stated: [t]he prosecution of significant traffickers of illegal drugs, including marijuana, and the disruption of illegal drug manufacturing and trafficking networks continues to be a core priority in the [Justice] Department's efforts against narcotics and dangerous drugs, and the Department's investigative and prosecutorial resources should be directed towards these objectives. As a general matter, pursuit of these priorities should not focus federal resources in your States on individuals whose actions are in clear and unambiguous compliance with existing state laws providing for the medical use of marijuana. In a follow-up memorandum to U.S. Attorneys, former Deputy Attorney General James Cole restated that enforcing the CSA remained a core priority of DOJ, even in states that had legalized medical marijuana. He clarified that "[t]he Ogden Memorandum was never intended to shield such activities from federal enforcement action and prosecution, even where those activities purport to comply with state law." In his memo, Deputy Attorney General Cole warned those who might assist medical marijuana dispensaries in any way. He stated that "[p]ersons who are in the business of cultivating, selling or distributing marijuana, and those who knowingly facilitate such activities [emphasis added], are in violation of the Controlled Substances Act, regardless of state law." This has been interpreted by some to mean, for example, that building owners and managers are in violation of the CSA by allowing medical marijuana dispensaries to operate in their buildings. Deputy Attorney General Cole further warned that "[t]hose who engage in transactions involving the proceeds of such activity [cultivating, selling, or distributing of marijuana] may be in violation of federal money laundering statutes and other federal financial laws." This warning may be one reason why medical marijuana dispensaries have had difficulty accessing bank services. In an August 2013 memorandum, Deputy Attorney General Cole stated that while marijuana remains an illegal substance under the CSA, DOJ would focus its resources on the "most significant threats in the most effective, consistent, and rational way." The memo outlined eight enforcement priorities for DOJ: Preventing the distribution of marijuana to minors; Preventing revenue from the sale of marijuana from going to criminal enterprises, gangs, and cartels; Preventing the diversion of marijuana from states where it is legal under state law in some form to other states; Preventing state-authorized marijuana activity from being used as a cover or pretext for the trafficking of other illegal drugs or other illegal activity; Preventing violence and the use of firearms in the cultivation and distribution of marijuana; Preventing drugged driving and the exacerbation of other adverse public health consequences associated with marijuana use; Preventing the growing of marijuana on public lands and the attendant public safety and environmental dangers posed by marijuana production on public lands; and Preventing marijuana possession or use on federal property. In a February 2014 memorandum, Deputy Attorney General Cole further reinforced these enforcement priorities, specifically as they relate to the prosecution of marijuana-related financial crimes. The memo directed the U.S. Attorneys that "in determining whether to charge individuals or institutions with ... [certain financial] offenses based on marijuana-related violations of the CSA, prosecutors should apply the eight enforcement priorities described in the August 29 guidance." In October 2014, DOJ released another memo to the U.S. Attorneys that reiterated the applicability of the eight enforcement priorities to their marijuana efforts in Indian country. It responded to the American Indian tribes' requests for guidance on CSA enforcement on tribal lands. DOJ reiterated that the August 2013 Cole memo does not prohibit the federal government from enforcing federal law in Indian Country, and adds the following: The eight priorities in the Cole Memorandum will guide United States Attorneys' marijuana enforcement efforts in Indian Country, including in the event that sovereign Indian Nations seek to legalize the cultivation or use of marijuana in Indian Country [emphasis added]. Unlike the Cole memo, DOJ did not specifically refer to distribution and regulation of marijuana. It was unclear whether distribution of marijuana would be tolerated on tribal lands should tribal governments seek to legalize and distribute marijuana. Despite the lack of clarity, some tribes moved forward with plans to grow and sell marijuana at tribe-owned stores on tribal lands. Since the memo was released, the DEA has led marijuana enforcement actions on tribal lands, but it remains unclear whether legal marijuana will be tolerated on tribal land as it has been tolerated in states. In a review of the DOJ memoranda, the Government Accountability Office (GAO) concluded that "DOJ has not historically devoted resources to prosecuting individuals whose conduct is limited to possession of small amounts of marijuana for personal use on private property. Rather, DOJ has left such lower-level or localized marijuana activity to state and local law enforcement authorities through enforcement of their own drug laws." GAO has recommended that DOJ monitor the effects of state-level marijuana legalization initiatives relative to the eight DOJ enforcement priorities. This evaluation noted that DOJ has used a number of tools to help assess these effects. For instance, DOJ indicated to GAO that U.S. Attorneys were in contact with officials in states such as Colorado and Washington that had legalized marijuana. In addition, DOJ reported that it relies upon information from sources such as "federal surveys on drug use; state and local research; and feedback from federal, state, and local law enforcement." Notably, DOJ has reportedly not been documenting its specific monitoring process, and GAO has recommended that DOJ develop a "clear plan" for how it will monitor and document the effects of state marijuana legalization on federal enforcement priorities. Over the past several years, Congress has included provisions in appropriations acts that prohibit DOJ from using appropriated funds to prevent certain states and the District of Columbia from "implementing their own State laws that authorize the use, distribution, possession, or cultivation of medical marijuana." The current appropriations provision is in effect until April 28, 2017. Courts have interpreted the appropriation provision to restrict DOJ from using appropriated funds (1) to take legal action directly against states and (2) to initiate criminal prosecutions of state officials for any action related to the implementation of a state medical marijuana law. Several federal courts also have interpreted the provision as prohibiting DOJ from prosecuting individuals who, while strictly complying with the laws of one of the states covered by the appropriations provisions, have allegedly distributed, possessed, or cultivated medical marijuana in violation of federal law. Although the appropriations provision restricts DOJ's ability to expend funds to enforce federal law, at least one court has made clear that the provision "does not provide immunity from prosecution for federal marijuana offenses." As explained below, so long as marijuana remains classified as a Schedule I controlled substance under federal law, financial institutions and their directors, officers, employees, and owners could be subject to severe criminal and administrative sanctions for providing financial services to marijuana businesses, even if those businesses are operating in compliance with state law. A consequence of these legal risks is that many financial institutions reportedly have been unwilling to provide financial services to state-authorized marijuana businesses. Federal law classifies marijuana as a Schedule I controlled substance. As a result, it is a federal crime to grow, sell, or merely possess the drug. In addition to facing the prospect of a federal criminal prosecution, imprisonment, and criminal fines, those who violate the federal CSA may suffer a number of additional adverse consequences under federal law. For example, federal authorities may confiscate any property used to grow marijuana or facilitate its sale or use, as well as all proceeds derived from the sale of marijuana. When financial institutions provide financial services to business customers, they generally are not directly involved in the sale, possession, or distribution of their customers' products. However, financial institutions commonly acquire the proceeds from the sale of their customers' products. To the extent that a bank acquires such proceeds with the knowledge that they are derived from the sale of marijuana in violation of federal law, the proceeds potentially could be confiscated by federal authorities, even when the underlying actions are permissible under state law. For example, if a bank originates a loan to a business openly operating as a state-authorized medical marijuana dispensary, then the principal and interest payments earned by the bank on that loan could be subject to forfeiture, if the bank knew that those payments derived from the sale of marijuana in violation of federal law. In addition to the risk of asset forfeiture, federal anti-money laundering laws (i.e., Sections 1956 and 1957 of the criminal code) criminalize the handling of proceeds that are known to be derived from certain unlawful activities, including the sale and distribution of marijuana. Violators of these anti-money laundering laws may be subject to fines and imprisonment, and any real or personal property involved in or traceable to prohibited transactions is subject to criminal or civil forfeiture. For example, a bank employee could be subject to a 20-year prison sentence and criminal money penalties under Section 1956 for knowingly engaging in a financial transaction involving marijuana-related proceeds that is conducted with the intent to promote a further offense (e.g., withdrawing marijuana-generated funds in order to pay the salaries of medical marijuana dispensary employees). Similarly, a bank officer could face a 10-year prison term and criminal money penalties under Section 1957 for knowingly depositing or withdrawing $10,000 or more in cash that is derived from the distribution and sale of marijuana. Furthermore, Congress has crafted laws that affirmatively enlist financial institutions to aid in the investigation and prosecution of those who violate federal laws, including the CSA. For example, financial institutions generally must file suspicious activity reports (SARs) with the Treasury Department's Financial Crimes Enforcement Network (FinCEN) regarding financial transactions suspected to be derived from specified illegal activities, including the sale of marijuana. Depository institutions and certain other financial institutions also must establish and maintain anti-money laundering programs, designed to ensure that the institutions' officers and employees will have sufficient knowledge of their customers and of the businesses of those customers to identify the circumstances under which filing SARs is appropriate. Even in the absence of suspicion, financial institutions must file currency transaction reports (CTRs) with FinCEN relating to transactions involving $10,000 or more in cash or other "currency." The failure to comply with these reporting requirements can result in fines and imprisonment. Additionally, financial institutions, their employees, and certain other affiliated parties could be subject to administrative enforcement actions by federal regulators for violating the Bank Secrecy Act or anti-money laundering laws. For example, the federal banking regulators may utilize administrative enforcement powers against depository institutions and their directors, officers, controlling shareholders, employees, agents, and affiliates that engage in unlawful, marijuana-related activities. The banking regulators have the legal authority, for instance, to issue cease and desist orders, impose civil money penalties, and issue removal and prohibition orders that temporarily or permanently ban individuals from working for any depository institution. The banking regulators also have the authority, under certain circumstances, to revoke an institution's federal deposit insurance coverage and to take control of and liquidate a depository institution. In fact, a criminal conviction for violating the Bank Secrecy Act or anti-money laundering laws is an explicit ground for the appointment of the Federal Deposit Insurance Corporation "as receiver [to] place the insured depository institution in liquidation." In response to state marijuana legalization efforts, FinCEN issued guidance with respect to marijuana-related financial crimes on February 14, 2014. This guidance appears to provide a roadmap for financial institutions seeking to comply with suspicious activity reporting requirements when providing financial services to state-authorized marijuana businesses, while also alerting FinCEN to transactions that might trigger federal enforcement priorities. The guidance notes that: [b]ecause federal law prohibits the distribution and sale of marijuana, financial transactions involving a marijuana-related business would generally involve funds derived from illegal activity. Therefore, a financial institution is required to file a SAR on activity involving a marijuana-related business (including those duly licensed under state law) in accordance with this guidance and [FinCEN regulations]. FinCEN advised financial institutions that, in providing services to a marijuana business, they must file one of three types of special SARs: 1. A marijuana limited SAR: The marijuana limited SAR is seen to be appropriate when the bank determines, after the exercise of due diligence, that a customer is not engaged in any activities that violate state law or implicate the investigation and prosecution priorities in the 2014 Cole Memorandum (see " Department of Justice Guidance Memos for U.S. Attorneys "); 2. A marijuana priority SAR: A marijuana priority SAR must be filed when the financial institution believes a customer is engaged in activities that implicate DOJ's investigation and prosecution priorities; and 3. A marijuana termination SAR: A financial institution is instructed to file a marijuana termination SAR when it finds it necessary to sever its relationship with a customer to maintain an effective anti-money laundering program. FinCEN also provides examples of "red flags" that may indicate that a marijuana priority SAR is appropriate. The FinCEN guidance does not impact financial institutions' obligations to file currency transaction reports. While the majority of the American public supports marijuana legalization, some have voiced concern over possible negative implications, particularly with respect to recreationa l legalization. Some concerns were outlined as enforcement priorities by DOJ in monitoring state legalization. These implications include, but are not limited to, the potential impact of legalization on (1) use of marijuana, particularly among youth; (2) traffic-related incidents involving marijuana-impaired drivers; (3) trafficking of marijuana from states that have legalized it into neighboring states that have not; and (4) U.S. compliance with international treaties. On the other hand, some have been encouraged by the potential outcomes from marijuana legalization, including new tax revenue for states and a potential decrease in marijuana-related arrests. Not all potential implications are discussed in this report, and some are yet to be fully measured. Of note, data on potential effects of marijuana legalization should be interpreted with caution, as they are fairly limited, and not all factors are presented when reporting changes in statistics since state legalization. Further, conclusions about the impact of marijuana legalization would be premature without broader inclusion of both historical data and additional years of post-legalization data, as well as consideration of other factors aside from legalization. As discussed, marijuana is the most commonly used illicit drug in the United States. In 2015, an estimated 22.2 million individuals aged 12 or older were current (past month) users of marijuana. The percentage of users has gradually increased over the last several years—from 6.9% in 2010 to 8.3% in 2015. The rate of past-month marijuana use among youth (aged 12 to 17), however, has remained fairly unchanged over this period (7.0%). In the states that legalized recreational marijuana in November 2012 (Washington and Colorado), the percentages of youth (aged 12-17) and adults (aged 18 and older) who are current users have changed in various ways over the 2010-2015 period according to survey data. For adults, the changes generally match national trends over the same time period (see Figure 3 ). Colorado and Washington have higher percentages of use for adults and youth compared to national estimates—both before and after recreational legalization began. Of note, the 2014/2015 percentages of marijuana use among youth are fairly similar to the percentages reported in 2010/2011, while adult percentages are higher than those reported in 2010/2011. Rates of drug use may be influenced by many possible factors including availability of the drug, family, peers, school, economic status, and community variables. Of note, some state government officials in states that have legalized marijuana have monitored changes in drug use patterns and emerging research on the health effects of marijuana. For example, the Colorado Department of Public Health and Environment (CDPHE) was given the responsibility to "monitor changes in drug use patterns, broken down by county and race and ethnicity, and the emerging science and medical information relevant to the health effects associated with marijuana use." The recent use of marijuana has been shown to impair driving ability. According to the National Highway Traffic Safety Administration (NHTSA), "[l]ow doses of THC moderately impair cognitive and psychomotor tasks associated with driving, while severe driving impairment is observed with high doses, chronic use and in combination with low doses of alcohol." Some may be concerned that recreational marijuana legalization could be associated with an increase in marijuana-related traffic incidents. In Colorado, despite limited traffic data, the Department of Public Safety reports the following: [T]he number of summons issued for Driving Under the Influence [DUI] in which marijuana or marijuana-in-combination[ ] with other drugs [was recorded] decreased 1% between 2014 and 2015 (674 to 665). The prevalence of marijuana or marijuana-in-combination identified by CSP [Colorado State Patrol] as the impairing substance increased from 12% of all DUIs in 2014 to 15% in 2015. The Denver Police Department found summons where marijuana or marijuana‐in-combination was recorded increased from 33 to 73 between 2013 and 2015. Citations for marijuana or marijuana‐in‐combination account for about 3% of all DUIs in Denver. Toxicology results from Chematox Laboratory showed an increase in positive cannabinoid screens for drivers, from 57% in 2012 to 65% in 2014. Of those that tested positive on the initial screen, the percent testing positive for delta‐9 Tetrahydrocannabinol (THC) at 2 nanograms/millileter rose from 52% in 2012 to 67% in 2014. Fatalities with THC‐only or THC‐in‐combination positive drivers increased 44%, from 55 in 2013 to 79 in 2014. Note that the detection of any THC in [the] blood is not an indicator of impairment but only indicates presence in the system. Detection of delta‐9 THC, one of the psychoactive properties of marijuana, may be an indicator of impairment. In monitoring the impacts of recreational marijuana legalization in Washington State, government researchers report that there was no trend identified in the percentage of drivers testing positive for marijuana (either marijuana only or marijuana in combination with other drugs/alcohol) for those involved in traffic fatalities and who were tested for drugs or alcohol. They also report that "marijuana incidents" on the highways and roads decreased from 2,462 in 2012 to 625 in 2014. Changes in these data may be influenced by many possible factors including changes in enforcement practices and priorities. It is possible that the sharp drop in marijuana incidents may be explained by the legalization of marijuana possession after 2012. For example, many traffic stops involving the smell of marijuana would no longer require further law enforcement investigation unless the individual in question is under the age of 21, there is suspicion of drug trafficking, or other reasons. After the legalization of the possession, sale, manufacturing, and distribution of certain quantities of marijuana for recreational purposes, one might expect the number of marijuana arrests to go down in jurisdictions that have done so. Indeed, Washington State reports that "all criminal activities involving marijuana decreased between 2012 and 2014." Possession was cited as the most common criminal activity, and the number of marijuana possession arrests decreased from 5,133 in 2012 to 2,091 in 2013, and then to 1,918 in 2014. Additionally, the number of marijuana incidents decreased from 6,336 in 2012 to 2,326 in 2014. In Colorado, the number of marijuana arrests decreased by nearly half from 12,894 in 2012 to 6,502 in 2013, and then increased to 7,004 in 2014. Of note, the number of marijuana arrests for youth (aged 10-17) increased by 6%, from 3,235 in 2012 to 3,400 in 2014, after a slight decline in 2013. Mexican transnational criminal organizations have historically been the primary foreign suppliers of marijuana to the United States, with small amounts also coming from Canada and the Caribbean. While anecdotal reports about the impact of domestic legalization initiatives on the domestic marijuana black market exist, officials have noted that there is an "intelligence gap" with respect to data on exactly how domestic legalization has impacted the amount of Mexican-produced marijuana entering the United States. For one, estimates on domestic marijuana consumption cannot speak to the source of this marijuana. In addition, drug seizure data from the various federal, state, and local law enforcement agencies do not give a sense of the origin of the marijuana. Further, there is no marijuana "signature program," like there is for cocaine and heroin, that can help determine the geographic origin of cannabis plants used to produce the seized marijuana. Marijuana cultivation in Mexico has decreased, though it is unclear precisely how this affects or is driven by U.S. demand for Mexican marijuana. One of the tradeoffs has been an increase in production of other drugs. Reportedly, the trafficking organizations have shifted production to more profitable drugs such as heroin and methamphetamine. Consistent with a decline in Mexican marijuana cultivation, there has been a general decline in marijuana seizures along the Southwest border between 2010 and 2015. However, the DEA's outlook on marijuana trafficking is that "Mexico-produced marijuana will continue to be trafficked into the United States in bulk quantities and will likely increase in quality to compete with domestically-produced marijuana." One notable statistic is that since the first states began legalizing marijuana for recreational use in 2012, there has been a "sharp decline" in the number of individuals prosecuted and sentenced for federal marijuana trafficking offenses. As experts have noted, however, this decline could be driven by a number, or combination, of factors such as federal efforts to prosecute marijuana-related drug offenders, efforts by drug traffickers to conceal their illegal contraband entering the United States, and the amount of illegal marijuana being shipped into the United States. Some states have alleged that there has been increased marijuana trafficking from nearby states that have legalized marijuana possession or sale for medical or recreational purposes. For instance, according to DEA testimony, there has been increased marijuana trafficking in states surrounding Colorado since the state legalized recreational use. The Rocky Mountain High Intensity Drug Trafficking Area (HIDTA) reported 394 instances of interdiction of Colorado marijuana destined for 36 other states in 2015. Additionally, the HIDTA's report indicates that interdiction experts estimate these seizures represent about 10% or less of the total amount that is moved across the border undetected. In December 2014, Nebraska and Oklahoma filed a lawsuit in the U.S. Supreme Court against Colorado claiming that their law enforcement and criminal justice systems had been adversely impacted by Colorado's laws legalizing marijuana. The complaint included claims that Colorado's "statutes and regulations are devoid of safeguards to ensure marijuana cultivated and sold in Colorado is not trafficked to other states." In March 2016, however, the Supreme Court declined to hear the case challenging Colorado's marijuana law. There have been reports of changes in the domestic black market for marijuana as states have moved to legalize it for medical and recreational purposes. For instance, the market in Denver, CO, has been described as smaller and less violent than it previously was. In addition, buyers there are said to be purchasing more from "mom-and-pop operations" rather than from entities affiliated with larger cartels. Most of the domestically produced marijuana (other than that which is produced in accordance with various state laws) is cultivated in California. This cultivation is carried out not only by U.S. persons, but also by foreign criminal networks. For instance, Mexican traffickers run large outdoor grow sites in California, which are sometimes established on public lands. The DEA has indicated that marijuana concentrates—such as hashish, hash oil, and keif—are a growing concern for federal law enforcement. These substances have "potency levels far exceeding those of leaf marijuana." The DEA has also stated that one effect of state marijuana legalization initiatives has been an increase in seizures of marijuana concentrates and an increase in the number of THC extraction laboratories in the United States. Broadly, there has been a shifting demand for higher-quality marijuana. The marijuana produced in the United States and Canada is generally thought to be of superior quality to the marijuana produced in Mexico. To be responsive to the U.S. demand for high-quality marijuana, Mexican drug traffickers have tried to improve their product. However, it is not just U.S. consumers who demand higher-quality marijuana. The demand exists in Mexico as well; there have even been anecdotal reports of traffickers moving high-quality marijuana produced in the United States across the Southwest border for sale and distribution in Mexico. U.S. officials have not yet reported data on the quantity or frequency of this southbound smuggling. In Colorado, state law allows the cultivation of up to 99 marijuana plants for patients and caregivers and up to 6 plants per individual for recreational purposes. In what has been dubbed "the gray market," marijuana is sometimes being grown legally but then sold illegally. In addition to federal and local enforcement actions against gray market actors, Colorado Governor Hickenlooper reportedly is seeking to establish new limits on residential plants and give law enforcement additional resources to combat unlicensed marijuana growers. A number of criminal networks rely on profits generated from the sale of illegal drugs—including marijuana—in the United States. Mexican drug trafficking organizations control more of the wholesale distribution of marijuana than other major drug trafficking organizations in the United States. One estimate has placed the proportion of U.S.-consumed marijuana that was imported from Mexico at somewhere between 40% and 67%. While the Mexican criminal networks control the wholesale distribution of illicit drugs in the United States, they "are not generally directly involved in retail distribution of illicit drugs." In order to facilitate the retail distribution and sale of drugs in the United States, Mexican drug traffickers have formed relationships with U.S. street, prison, and outlaw motorcycle gangs. Although these gangs have historically been involved with retail-level drug distribution, their ties to the Mexican criminal networks have allowed them to become increasingly involved at the wholesale level as well. Trafficking and distribution of illicit drugs is a primary source of revenue for these gangs. A number of organizations have assessed the potential profits generated from illicit drug sales, both worldwide and in the United States, but "[e]stimates of marijuana ... revenues suffer particularly high rates of uncertainty." The former National Drug Intelligence Center (NDIC), for instance, estimated that the sale of illicit drugs in the United States generates between $18 billion and $39 billion in U.S. wholesale drug proceeds for the Colombian and Mexican drug trafficking organizations annually. The proportion that is attributable to marijuana sales, however, is unknown. Without a clear understanding of (1) actual proceeds generated by the sale of illicit drugs in the United States, (2) the proportion of total proceeds attributable to the sale of marijuana, and (3) the proportion of marijuana sales controlled by criminal organizations and affiliated gangs, any estimates of how marijuana legalization might impact the drug trafficking organizations are purely speculative. Marijuana proceeds are generated at many points along the supply chain, including production, transportation, and distribution. Experts have debated which aspects of this chain—and the related proceeds—would be most heavily impacted by marijuana legalization. In addition, the potential impact of marijuana legalization in some subset of the states (complicated by varying legal frameworks and regulatory regimes) may be more difficult to model than the impact of federal marijuana legalization. For instance, in evaluating the potential fiscal impact from the 2012 Washington and Colorado legalization initiatives on the profits of Mexican drug trafficking organizations, the Organization of American States (OAS) hypothesized that "[a]t the extreme, Mexican drug trafficking organizations could lose some 20 to 25 percent of their drug export income, and a smaller, though difficult to estimate, percentage of their total revenues." Other scholars have based their estimates on a hypothetical federal legalization of marijuana when estimating the potential financial impact of marijuana legalization. Under this scenario, small-scale growers at the start of the marijuana production-to-consumption chain might be put out of business by professional farmers, a few dozen of which "could produce enough marijuana to meet U.S. consumption at prices small-scale producers couldn't possibly match." Large drug trafficking organizations generate a majority of their marijuana-related income (which some estimates place at between $1.1 billion to $2.0 billion) from exporting the drug to the United States and selling it to wholesalers on the U.S. side of the border. This revenue could be jeopardized if the United States were to legalize the production and consumption of recreational marijuana. Of note, the Tax Foundation has estimated that the annual U.S. marijuana market is $45 billion—0.28% of GDP. Under a legalization regime, some portion of the revenue that might have previously been generated by traffickers could be lost to authorized sellers (in the form of profits) and governments (in the form of taxes). Developments in state marijuana laws and policies, particularly those that relate to recreational marijuana activities, have raised some concerns about the United States' compliance with three United Nations (U.N.) drug control treaties that impose certain international obligations relating to marijuana. These treaties generally seek to curb the use of controlled substances while carving out exceptions for medicinal and scientific uses. The United States is a party to the following drug treaties: The Single Convention on Narcotic Drugs (Single Convention) requires parties to the convention to "take such legislative and administrative measures as may be necessary ... to limit exclusively to medical and scientific purposes" the manufacture, distribution, trade, use, and possession of "cannabis." The 1971 Convention on Psychotropic Substances requires that specific controls be placed upon THC. The 1988 U.N. Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances requires parties to establish criminal penalties for the possession, purchase, or cultivation of marijuana for nonmedicinal consumption, but only to the extent that such action is consistent with the "constitutional principles and basic concepts of [the country's] legal system." The International Narcotics Control Board (INCB or Board) and the Commission on Narcotic Drugs of the Economic and Social Council (Commission) are responsible for monitoring parties' compliance with these treaties, though they appear to have limited ability to enforce such compliance. For example, the Single Convention provides that the Commission may "call the attention of the Board to any matters which may be relevant to the functions of the Board," while the Board may take measures that are "most consistent with the intent to further the co-operation of Governments with the Board and to provide the mechanism for a continuing dialogue between Governments and the Board which will lend assistance to and facilitate effective national action to attain the aims of this Convention." It is unclear whether, or to what extent, the enactment of state laws authorizing the use of marijuana for recreational purposes affects the United States' compliance with the drug treaties. Some assert that state-level recreational marijuana legalization (and the federal government response to those state laws) does not conform with the international obligations regarding marijuana, while others disagree with this interpretation. For example, the then-President of the INCB stated in 2013 that recreational marijuana legalization in states is inconsistent with the Single Convention's requirement that parties limit lawful uses of cannabis to medical and scientific purposes. On the other hand, in 2014, the then-Assistant Secretary of State for International Narcotics and Law Enforcement Affairs appeared to express a contrary view when he urged the international community to "accept flexible interpretation of" the U.N. Drug Control Conventions. He appealed to countries "to tolerate different national drug policies, to accept the fact that some countries will have very strict drug approaches; other countries will legalize entire categories of drugs." A Stanford University professor has also opined that the United States is not in violation of the drug control conventions on account of state-level laws, although a Brookings Institution fellow has argued otherwise. Some observers have raised doubts about claims that the drug treaties contain the "flexibilities" that can accommodate state recreational marijuana laws; they have instead argued for reforms of the treaties to expressly permit them. Yet in September 2014, President Obama disagreed that the international drug control regime needs revision in light of marijuana policy developments. The Trump Administration's stance on this issue has not yet been articulated. All eight of the states that have legalized marijuana for recreational purposes levy some combination of taxes and business licensing fees at the level of marijuana cultivation or retail sales (in addition to general state sales taxes). Tax rates on the cultivation and retail sales are more commonly levied on an ad valorem basis, or as a percentage of price. The tax treatment of medical marijuana varies by state. In some states, medical marijuana is indirectly taxed further back the distribution chain at the cultivator level. In addition, states tax the retail sales of medical marijuana differently. In Colorado, for example, medical marijuana sales are exempt from a 10% special excise tax that applies to recreational marijuana sales, but they are still subject to the 2.9% general state sales tax. In Washington, medical marijuana sales are subject to the same 37% excise tax that applies to recreational sales, but they are exempt from the state's 6.5% general sales tax. While some states utilize marijuana-related revenue streams for general spending purposes, others have approved measures to dedicate a portion of this revenue for spending on education (Colorado and Oregon), criminal justice programs (Alaska), or public health and substance abuse programs (Washington). Overall, though, these tax and spending regimes have been subject to change, as government officials and voters respond to changes in revenue collections and budget priorities. Given the current federal marijuana policy gap with certain states, there are a number of issues that Congress may address. These include, but are not limited to, issues surrounding financial services for marijuana businesses, federal tax issues for these businesses, oversight of federal law enforcement, allowance of states to implement medical marijuana laws and involvement of federal health care workers, and consideration of marijuana's designation as a Schedule I drug. In spite of the guidance issued by FinCEN and DOJ, many financial institutions remain reluctant to openly enter relationships with state-authorized marijuana businesses. Some marijuana businesses and marijuana industry proponents have complained that even when marijuana businesses are able to open bank accounts or secure other financial services, those customer relationships are frequently terminated in relatively short order, especially when the existence of the relationship between the financial institution and the marijuana business becomes public. Over the years, several legislative proposals have been designed to jump-start financial relationships with state-authorized marijuana businesses. Some of these proposals would attempt to alleviate BSA reporting burdens beyond the measures detailed in the 2014 FinCEN guidance. These proposals also would amend banking laws to prevent banking regulators from "prohibit[ing], penaliz[ing], or otherwise discourag[ing] a depository institution from providing financial services to a marijuana-related legitimate business" (i.e., one that is in compliance with a state or local marijuana regulatory regime). While such measures, if enacted, might help around the edges, many financial institutions and their federal regulators may remain apprehensive about ties to the marijuana industry while marijuana is listed as a Schedule I controlled substance under the CSA. In the absence of legislative change to the CSA, financial institutions must proceed with the knowledge that the Administration could reverse or otherwise make significant changes to its enforcement priorities and policies. In other words, while these financial institutions may not be the subject of law enforcement investigations currently, the option remains. Other legislative proposals would reclassify marijuana as a Schedule II substance—this would legalize marijuana for medical purposes. This would likely do more to ease bank concerns with providing financial services to medical marijuana businesses but would not entirely eliminate a financial institution's legal risks, particularly if it associates with medical marijuana businesses that operate in states or localities lacking strong regulatory oversight and enforcement standards. Additionally, the reclassification of marijuana to Schedule II probably would have little impact on the provision of financial services to recreational marijuana businesses because they would still be operating in violation of the CSA. Marijuana producers and retailers may not deduct the costs of selling their product (e.g., payroll, rent, or advertising) for the purposes of the federal income tax filings. The Internal Revenue Code (IRC) Section 280E states that No deduction or credit shall be allowed for any amount paid or incurred during the taxable year in carrying on any trade or business if such trade or business (or the activities which comprise such trade or business) consists of trafficking in controlled substances (within the meaning of schedule I and II of the Controlled Substances Act) which is prohibited by Federal law or the law of any State in which such trade or business is conducted. Media reports indicate that the Internal Revenue Service (IRS) has enforced Section 280E in audits of marijuana-related businesses by refusing to accept these businesses' deductions. IRC Section 280E does not prohibit a marijuana business from deducting the costs of cultivating or acquiring marijuana as a "cost of goods sold," though. Effectively this constitutes an implicit tax on marijuana-related businesses equal to the value of the tax benefit of such deductions if these firms had engaged in an industry that was legal under federal law. One such public case involves the Sacramento-based Canna Care marijuana dispensary. The IRS disallowed $2.6 million in deductions for employee salaries, rent, and other costs over a three-year period, which resulted in the business owing $875,000 in additional taxes. Canna Care challenged the IRS in U.S. Tax Court, but ultimately the court upheld the IRS ruling. The discrepancies between federal, state, and local tax treatments of marijuana-related businesses may create economic incentives to engage in the underground economy. In addition to the uncertainty of federal tax enforcement procedures (and costs of any related legal assistance), the inability of marijuana businesses to deduct their business expenses is effectively an implicit tax up to 39.6% (if organized as sole-proprietor or partnership) or 35% (if organized as a C corporation) of the cost of these expenses. These implicit taxes are paid in addition to state and local sales and special excise taxes. The status quo administration of federal tax laws creates an economic advantage for illicit marijuana sellers, who are not subject to direct taxation of their sales. Past marijuana-related tax proposals have varied in scope. Some would have exempted a business (that conducts marijuana sales in compliance with state law) from the Section 280E prohibition against allowing business-related tax credits or deductions for expenditures in connection with trafficking in controlled substances. In contrast, one bill would have removed marijuana from all lists of controlled substances (and, indirectly, IRC §280E restrictions on marijuana), and another would have imposed a federal excise tax on domestic recreational marijuana retail sales that would begin at 10% of the price and phase in a tax rate of 25% over four years. In exercising its oversight authorities, Congress may choose to examine the extent to which (if at all) federal law enforcement missions—in particular the DEA's mission—are impacted by state legalization of marijuana. For instance, policymakers may elect to review the mission of each federal law enforcement agency involved in enforcing the CSA and examine how its drug-related investigations may be influenced by the varying state-level policies regarding marijuana. As noted, federal law enforcement has generally prioritized the investigation of drug traffickers and dealers over that of low-level drug users. Policymakers may question whether these policies and priorities are implemented consistently across states with different drug policies regarding marijuana. One issue policymakers may debate is whether or how to incentivize task forces, fusion centers, and other coordinating bodies charged with combating drug-related crimes. Before determining whether to increase, decrease, or maintain funding for coordinated efforts such as task forces, policymakers may consider whether state and local counterparts are able to effectively achieve task force goals if the respective state marijuana policy is not in agreement with federal marijuana policy. Policymakers may choose to evaluate whether certain drug task forces are sustainable in states that have established policies that are either inconsistent—such as in states that have decriminalized small amounts of marijuana possession—or are in direct conflict—including states that have legalized either medical or recreational marijuana—with federal drug policy. For instance, might there be any internal conflicts that prevent task force partners from collaborating effectively to carry out their investigations? Of note, the Arizona Court of Appeals ruled that patients who possess marijuana in compliance with the Arizona Medical Marijuana Act are entitled to the return of their marijuana that law enforcement may have seized during a traffic stop. In states such as Colorado, media reports indicate that some local law enforcement officers avoid seizing marijuana in certain cases because they do not want to have to return the marijuana to its owner—an act that is tantamount to distribution of a Schedule I controlled substance, a violation of federal law. As noted, in responding to states with recreational legalization initiatives, DOJ issued federal enforcement priorities for states with legal marijuana. According to DOJ, it monitors the effects of state legalization by collaborating with other DOJ components and other federal agencies in assessment of marijuana enforcement-related data; prosecuting cases that threaten federal enforcement priorities; and consulting with state officials about areas of federal concern. As of December 2015, however, DOJ has not documented its efforts to monitor the effects of state legalization and ensure that these priorities are being emphasized. It is unclear how the metrics to evaluate these priorities will be used to determine whether federal intervention is needed in states that have legalized. For example, one of the eight enforcement priorities listed by Deputy Attorney General Cole was to prevent the diversion of marijuana to other states. While it seems the DEA is aware of increased marijuana trafficking from Colorado to Kansas, it is unclear what level of increased trafficking might trigger action by the federal government against state marijuana laws. Congress may choose to exercise oversight over DOJ's enforcement priorities and metrics for tracking illicit activity in the states. Congress may also request research on or an investigation of this issue outside of actions by the Administration. The Administration may alter or reverse its enforcement priorities at any time. As mentioned, in a February 2017 White House press statement, the Trump Administration indicated there may be increased enforcement against recreational marijuana, and stated that there is a "big difference" between medical and recreational marijuana. State medical marijuana laws have raised questions for federal policymakers about enforcing federal law related to marijuana in situations where individuals or organizations are acting in compliance with state law. In previous Congresses, Members of both the House and the Senate have introduced legislation that would amend the CSA such that provisions relating to marijuana would not apply to a person who is acting in compliance with relevant state law. As discussed, in recent years, Congress has included policy riders in appropriations acts to prohibit DOJ from using funds to prevent states from implementing their medical marijuana laws. Congress may decide to alter, maintain, or reverse this provision. Notably, in a February 2017 White House press statement, the Trump Administration signaled some acceptance of the medicinal use of marijuana: "[t]he President understands the pain and suffering that many people go through who are facing especially terminal diseases and the comfort that some of these drugs, including medical marijuana, can bring to them." A topic of particular interest to federal policymakers has been how federal health care providers—especially those in the Department of Veterans Affairs (VA)—deal with state medical marijuana laws. VA policy does not deny health care services to veterans who participate in state marijuana programs; however, it does prohibit VA providers from completing the forms that effectively take the place of prescriptions in state medical marijuana programs. Members in both chambers have introduced legislation that would allow VA providers to complete such forms. Similar provisions passed the Senate as part of an FY2016 appropriations bill, and passed the Senate Committee on Appropriations as part of an FY2017 appropriations bill; however, neither were included in an enacted appropriations law. As the gap between federal and state policies on marijuana widens each year, policymakers might decide to reevaluate federal marijuana policy. It has only been a few years since states began to legalize recreational marijuana, but over 20 years since they began to legalize medical marijuana. A large majority of states now have marijuana policies that contradict the CSA. In addressing state-level legalization efforts, Congress could take one of several routes. It could elect to take no action, thereby upholding the federal government's current marijuana policy and enforcement priorities. It may also decide that the CSA must be enforced in states and direct federal law enforcement to strictly enforce the CSA, even when individuals may be in compliance with state laws. Alternatively, Congress could choose to reevaluate marijuana's placement as a Schedule I controlled substance. Given the history of its scheduling, Congress may consider establishing a committee of experts to evaluate the efficacy of marijuana laws in the United States and address other issues such as the medicinal value and harm of marijuana use. Upon reevaluation, should Congress determine that marijuana no longer meets the criteria to be a Schedule I substance, it could take legislative action to remove it from the list of substances on that schedule. In doing so, Congress may (1) place marijuana on one of the other schedules (II, III, IV, or V) of controlled substances or (2) remove marijuana as a controlled substance altogether. If Congress chooses to remove marijuana as a controlled substance, it could alternatively seek to regulate and tax commercial marijuana activities. If marijuana remains a controlled substance under the CSA under any schedule, this would not eliminate the existing conflict with states that have legalized recreational marijuana. If the conflict remains, Congress may choose to continue to allow states to carry on with implementation of recreational marijuana laws, or it may choose to press for increased enforcement action against or within the states to attempt to stop state-sanctioned, recreational marijuana. Appendix A. Medical Research on Marijuana Approved Drugs and Ongoing Research The Food and Drug Administration (FDA) has approved two drugs containing synthetic THC: nabilone and dronabinol. Nabilone is FDA-approved as an antiemetic (to reduce nausea or prevent vomiting) for patients receiving chemotherapy for cancer. Dronabinol is FDA-approved as both an antiemetic for patients on chemotherapy and an appetite stimulant for patients with AIDS-related weight loss. In addition, drugs containing plant-derived THC and/or cannabidiol (CBD, a nonpsychoactive chemical component of marijuana) are in the drug development and approval process. The UK-based GW Pharmaceuticals has plant-derived cannabinoid drug products in trials with the goal of FDA approval. Its drug Sativex®, which is composed primarily of plant-derived THC and CBD, has already gained approval in 30 other countries for the treatment of spasticity due to multiple sclerosis. In 2014, the company announced that the FDA had granted "Fast Track" designation to Sativex as a potential pain reliever for patients with advanced cancer; however, in 2015, three trials of Sativex failed to show superiority over a placebo. The company continues to seek approval of Sativex and other plant-derived cannabinoid products for treatment of various conditions (e.g., childhood epilepsy). Scientific Evaluations of Marijuana Recent evaluations conducted separately by the FDA and the National Academies of Sciences, Engineering, and Medicine (the National Academies) illustrate the challenge of meeting the required standard of evidence. While taking different approaches to their evaluations, both the FDA and the National Academies have found that the current evidence base falls short. FDA Evaluation. The FDA evaluated only marijuana, not drugs containing a plant-derived chemical constituent of marijuana or drugs containing synthetic THC. Its analysis of marijuana's potential therapeutic effects is limited to 11 published studies that met criteria for inclusion in the review (e.g., that the study must be a randomized controlled trial). The studies examined marijuana's use to treat neuropathic pain (five studies), stimulate appetite in patients with HIV (two studies), treat glaucoma (two studies), treat spasticity in multiple sclerosis (one study), and treat asthma (one study). The evaluation also assessed potential risks of marijuana use (see text box, "Risks Associated with Marijuana Use"). The evaluation, called an eight-factor analysis, was conducted by the FDA pursuant to a request by the DEA. The DEA requests such scientific and medical evaluations from the Secretary of Health and Human Services (HHS) in response to petitions asking the DEA to reschedule marijuana administratively. National Academies Evaluation. The National Academies evaluated cannabis, its constituents, and drugs containing synthetic THC. For each of 11 health topics, the report assessed "fair- and good-quality" research, relying on systematic reviews published since 2011 (where available) and primary research published after the systematic review (or since 1999, if no systematic review exists). The 11 health topics are (1) therapeutic effects; (2) cancer; (3) cardiometabolic risk; (4) respiratory disease; (5) immunity; (6) injury and death; (7) prenatal, perinatal, and postnatal exposure to cannabis; (8) psychosocial effects; (9) mental health; (10) problem cannabis use; and (11) cannabis use and abuse of other substances. The report presents nearly 100 conclusions, including some related to the challenges in conducting research with cannabis and cannabinoids. Federal Research Requirements for Marijuana Many federal research requirements are standard across all schedules of controlled substances; however, some requirements vary according to the assigned schedule of the particular substance. Federal regulations are more stringent for Schedule I substances—including marijuana. Examples of this include the following: For Schedule I substances, such as marijuana, even if practitioners have a DEA registration for a substance in Schedules II-V, they must obtain a separate DEA registration for Schedule I substances. Individuals who seek to register to manufacture a controlled substance in Schedule I or II are subject to production quota limitations as determined by the DEA, but registrants for substances in Schedules III-V are not subject to such quotas. Researchers are required to store Schedule I and II substances in electronically monitored safes, steel cabinets, or vaults that meet or exceed certain specifications. They are required to store Schedule III-V substances by secure standards but the requirements are less stringent than those required for Schedule I and II substances. When researchers apply for a DEA registration to conduct research involving Schedule I controlled substances, they must comply with federal regulations specifying the form and content of the research protocols. The DEA Administrator must forward a copy of the application and research protocol to HHS, which is responsible for determining "the qualifications and competency of the applicant, as well as the merits of the protocol." The HHS Secretary delegates that responsibility to the FDA. No equivalent process is required for Schedule II -V controlled substances. Marijuana Supply for Researchers Under the CSA, the Attorney General is required to register an applicant to manufacture Schedule I or II controlled substances "if he determines that such registration is consistent with the public interest and with United States obligations under international treaties, conventions, or protocols in effect on May 1, 1971." In the case of marijuana, the National Center for Natural Products Research at the University of Mississippi has been the only registered manufacturer, operating under a contract administered by the National Institute on Drug Abuse (NIDA) within HHS's National Institutes of Health. For nearly 50 years, it has been the only official source through which researchers may obtain marijuana for research purposes—and which some have referred to as a "federal research monopoly." Some have contended that marijuana provided by NIDA to researchers is "both qualitatively and quantitatively inadequate." Marijuana's status as a Schedule I drug has reportedly created difficulty for researchers who seek to study the substance but are potentially unable to meet the strict requirements of the CSA, or perhaps they seek to utilize a different quality of marijuana than what is available through NIDA. In August 2016, the DEA announced a policy change "designed to foster research by expanding the number of DEA-registered marijuana manufacturers." Under the new policy, the DEA is willing to license additional growers to "operate independently, provided the grower agrees (through a written memorandum of agreement with DEA) that it will only distribute marijuana with prior, written approval from DEA." In addition, under the new policy, these growers will only be permitted to supply marijuana to DEA-registered researchers whose "protocols have been determined by [HHS] to be scientifically meritorious." This new approach, DEA states, will allow individuals to obtain a DEA cultivation registration "not only to supply federally funded or other academic researchers, but also for strictly commercial endeavors funded by the private sector and aimed at drug product development." Given that both the FDA and the DEA identified the lack of research as a significant factor in denying the rescheduling petitions in 2016, and to the extent that this policy may increase the amount of marijuana research conducted, the change could contribute to future debate on rescheduling. Appendix B. Background on Federal Marijuana Policy Early 20 th Century Prior to 1937, the growth and use of marijuana was legal under federal law. During the course of promoting federal legislation to control marijuana, Henry Anslinger, the first commissioner of the Federal Bureau of Narcotics (FBN), and others submitted testimony to Congress regarding the evils of marijuana use, claiming that it incited violent and insane behavior. Of note, Commissioner Anslinger had informed Congress that "the major criminal in the United States is the drug addict; that of all the offenses committed against the laws of this country, the narcotic addict is the most frequent offender." The federal government unofficially banned marijuana under the Marihuana Tax Act of 1937 (MTA; P.L. 75-238). The MTA imposed a strict regulation requiring a high-cost transfer tax stamp on marijuana sales, and these stamps were rarely issued by the federal government. Shortly after passage of the MTA, all states made the possession of marijuana illegal. Mid-20 th Century In the decades after enactment of the MTA, Congress continued to pass drug control legislation and further criminalized drug abuse. For example, the Boggs Act (P.L. 82-255), passed in 1951, established mandatory prison sentences for some drug offenses, while the 1956 Narcotic Control Act (P.L. 84-728) further increased penalties for drug offenses. In conjunction with growing support for a medical approach to addressing drug abuse, there was a strong emphasis on law enforcement control of narcotics. Congress shifted the constitutional basis for drug control from its taxing authority to its power to regulate interstate commerce, and in 1968 the FBN merged with the Bureau of Drug Abuse Control and was transferred from Treasury to the Department of Justice. Several years later, President Nixon would declare a war on drugs. Congress and President Nixon enhanced federal control of drugs in the enactment of comprehensive federal drug laws—including the Controlled Substances Act (CSA), enacted as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970 (P.L. 91-513). The CSA placed the control of marijuana and other plant, drug, and chemical substances under federal jurisdiction regardless of state regulations and laws. In designating marijuana as a Schedule I controlled substance, this legislation officially prohibited the manufacture, distribution, dispensation, and possession of marijuana. The Shafer Commission As part of the CSA, the National Commission on Marihuana and Drug Abuse, also known as the Shafer Commission, was established to study marijuana in the United States. Specifically, this commission was charged with examining issues such as (A) the extent of use of marihuana in the United States to include its various sources of users, number of arrests, number of convictions, amount of marihuana seized, type of user, nature of use; (B) an evaluation of the efficacy of existing marihuana laws; (C) a study of the pharmacology of marihuana and its immediate and long-term effects, both physiological and psychological; (D) the relationship of marihuana use to aggressive behavior and crime; (E) the relationship between marihuana and the use of other drugs; and (F) the international control of marihuana. The Shafer Commission, in concluding its review, produced two reports: (1) Marihuana: A Signal of Misunderstanding , and (2) Drug Use in America: Problem in Perspective . In its first report, the Shafer Commission discussed the perception of marijuana as a major social problem and how it came to be viewed as such. It made a number of recommendations, including the development of a "social control policy seeking to discourage marihuana use, while concentrating primarily on the prevention of heavy and very heavy use." In this first report, the commission also called the application of criminal law in cases of personal use of marijuana "constitutionally suspect" and declared that "total prohibition is functionally inappropriate." Of note, federal criminalization and prohibition of marijuana was never altered, either administratively or legislatively, to comply with the recommendations of the Shafer Commission. In its second report, the Shafer Commission reviewed the use of all drugs in the United States, not solely marijuana. It examined the origins of the country's drug problem, including the social costs of drug use, and once again made specific recommendations regarding social policy. Among other conclusions regarding marijuana, the commission indicated that aggressive behavior generally cannot be attributed to its use. The commission also reaffirmed its previous findings and recommendations regarding marijuana and added the following statement: The risk potential of marihuana is quite low compared to the potent psychoactive substances, and even its widespread consumption does not involve social cost now associated with most of the stimulants and depressants (Jones, 1973; Tinklenberg, 1971). Nonetheless, the Commission remains persuaded that availability of this drug should not be institutionalized at this time. At the conclusion of the second report, the Shafer Commission recommended that Congress launch a subsequent commission to reexamine the broad issues surrounding drug use and societal response. While a number of congressionally directed commissions regarding drugs have since been established, no such commission has been directed to review the comprehensive issues of drug use, abuse, and response in the United States.

Summary: Under federal law, the cultivation, possession, and distribution of marijuana are illegal, except for the purposes of sanctioned research. States, however, have established a range of laws and policies regarding marijuana's medical and recreational use. Most states have deviated from an across-the-board prohibition of marijuana, and it is now more so the rule than the exception that states have laws and policies allowing for some cultivation, sale, distribution, and possession of marijuana—all of which are contrary to the federal Controlled Substances Act (CSA). As of March 2017, nearly 90% of the states, as well as Puerto Rico and the District of Columbia, allow for the medical use of marijuana in some capacity. Also, eight states and the District of Columbia now allow for some recreational use of marijuana. These developments have spurred a number of questions regarding their potential implications for federal law enforcement activities and for the nation's drug policies as a whole. Thus far, the federal response to state actions to decriminalize or legalize marijuana largely has been to allow states to implement their own laws on marijuana. The Department of Justice (DOJ) has nonetheless reaffirmed that marijuana growth, possession, and trafficking remain crimes under federal law irrespective of states' positions on marijuana. Rather than targeting individuals for drug use and possession, federal law enforcement has generally focused its counterdrug efforts on criminal networks involved in the drug trade. While the majority of the American public supports marijuana legalization, some have voiced apprehension over possible negative implications. Opponents' concerns include, but are not limited to, the potential impact of legalization on (1) marijuana use, particularly among youth; (2) road incidents involving marijuana-impaired drivers; (3) marijuana trafficking from states that have legalized it into neighboring states that have not; and (4) U.S. compliance with international treaties. Proponents of legalization have been encouraged by potential outcomes that could result from marijuana legalization, including a new source of tax revenue for states and a decrease in marijuana-related arrests. Many of these potential implications are yet to be fully measured. Given the current marijuana policy gap between the federal government and many of the states, there are a number of issues that Congress may address. These include, but are not limited to, issues surrounding availability of financial services for marijuana businesses, federal tax treatment, oversight of federal law enforcement, allowance of states to implement medical marijuana laws and involvement of federal health care workers, and consideration of marijuana as a Schedule I drug under the CSA. The marijuana policy gap has widened each year for some time. It has only been a few years since states began to legalize recreational marijuana, but over 20 years since they began to legalize medical marijuana. In addressing state-level legalization efforts and considering marijuana's current placement on Schedule I, Congress could take one of several routes. It could elect to take no action, thereby upholding the federal government's current marijuana policy. It may also decide that the CSA must be enforced in states and not allow them to implement conflicting laws on marijuana. Alternatively, Congress could choose to reevaluate marijuana's placement as a Schedule I controlled substance.