In a strongly-worded new report out Tuesday, researchers at the Brookings Institution call on the federal government to eliminate roadblocks to medical marijuana research in the U.S.

"The federal government is stifling medical research in a rapidly transforming area of public policy that has consequences for public health and public safety," the report, authored by John Hudak and Grace Wallack, says. "Statutory, regulatory, bureaucratic, and cultural barriers have paralyzed science and threatened the integrity of research freedom in this area."

Noting that medical marijuana is already legal in dozens of states, the report argues that conflicting and contradictory federal policy is "interfering with the relationship between doctor and patient."

Even in states where medical marijuana is legal, doctors, patients and researchers often find themselves caught in a murky grey area between state and federal policy. Since 1972, the Drug Enforcement Administration has classified marijuana as a Schedule 1 controlled substance, meaning it has "no medically accepted use" and a "high potential for abuse."

Updating federal marijuana policy would likely need to start with re-scheduling the drug. Changing it to Schedule 2 would acknowledge a potential for medical use.

"Moving marijuana from Schedule I to Schedule II would signal to the medical community that FDA and NIH are ready to take medical marijuana research seriously, and help overcome a government-sponsored chilling effect on research that manifests in direct and indirect ways," Hudak and Wallack write.

In the past, anti-pot advocacy groups have argued against rescheduling, calling it "a symbolic victory for advocates who want to legalize marijuana." But academic researchers have long complained that federal restrictions on Schedule 1 drugs, including onerous registration and application requirements, make legitimate research "difficult and in many cases almost impossible."

In short, federal policy has created a "circular policy trap that hinders scientific research," according to Hudak and Wallack. Research into medical applications of marijuana is constrained by the Schedule 1 designation. And the plant is designated Schedule 1 because there isn't enough research into medical applications.

Marijuana could be rescheduled via a complicated petition process. Since marijuana was added to Schedule 1 in 1972, the government has been petitioned four times to remove or re-schedule the drug. The DEA denied three of the petitions, in some cases overriding the advice of federal judges, after wait times ranging from 6 to 20 years. A fourth petition, submitted by then-governors Christine Gregoire and Lincoln Chafee, has been under review by the DEA since 2011.

Given the DEA's long history of hostility toward marijuana reform, it seems unlikely that the current petition will fare any better. The quickest way to change the law, Hudak and Wallace write, may be through an act of Congress. The bipartisan CARERS act was introduced by Senators Cory Booker, Rand Paul and Kirsten Gillibrand earlier this year. It currently has 15 cosponsors from both parties.

While that bill would go a long way toward ending federal restrictions on marijuana research, Hudak and Wallack point out that there are other modest executive actions that Obama or his eventual successor could undertake as well. They include:

Ending the DEA-mandated monopoly on marijuana grown for research. Currently, all marijuana for federally-approved studies comes from a single lab at the University of Mississippi. "Because of this monopoly, research-grade drugs that meet researchers’ specifications often take years to acquire, if they are produced at all," the report argues.

Where cannabis is and isn't legal Show all 10 1 /10 Where cannabis is and isn't legal Where cannabis is and isn't legal UK Having been reclassified in 2009 from a Class C to a Class B drug, cannabis is now the most used illegal drug within the United Kingdom. The UK is also, however, the only country where Sativex – a prescribed drug that helps to combat muscle spasms in multiple sclerosis and contains some ingredients that are also found in cannabis - is licensed as a treatment Getty Where cannabis is and isn't legal North Korea Although many people believe the consumption of cannabis in North Korea to be legal, the official law regarding the drug has never been made entirely clear whilst under Kim Jong Un’s regime. However, it is said that the North Korean leader himself has openly said that he does not consider cannabis to be a drug and his regime doesn’t take any issue with the consumption or sale of the drug MARCEL VAN HOORN/AFP/Getty Images Where cannabis is and isn't legal Netherlands In the Netherlands smoking cannabis is legal, given that it is smoked within the designated ‘smoking areas’ and you don’t possess more than 5 grams for personal use. It is also legal to sell the substance, but only in specified coffee shops Getty Where cannabis is and isn't legal USA Although in some states of America cannabis has now been legalised, prior to the legalisation, police in the U.S. could make a marijuana-related arrest every 42 seconds, according to US News and World Report. The country also used to spend around $3.6 billion a year enforcing marijuana law, the American Civil Liberties Union notes AP Photo/Ted S. Warren Where cannabis is and isn't legal Spain Despite cannabis being officially illegal in Spain, the European hotspot has recently started to be branded, ‘the new Amsterdam’. This is because across Spain there are over 700 ‘Cannabis Clubs’ – these are considered legal venues to consume cannabis in because the consumption of the drug is in private, and not in public. These figures have risen dramatically in the last three years – in 2010 there were just 40 Cannabis Clubs in the whole of Spain. Recent figures also show that in Catalonia alone there are 165,000 registered members of cannabis clubs – this amounts to over 5 million euros (£4 million) in revenue each month Getty Where cannabis is and isn't legal Uruguay In December 2013, the House of Representatives and Senate passed a bill legalizing and regulating the production and sale of the drug. But the president has since postponed the legalization of cannabis until to 2015 and when it is made legal, it will be the authorities who will grow the cannabis that can be sold legally. Buyers must be 18 or older, residents of Uruguay, and must register with the authorities Getty Where cannabis is and isn't legal Pakistan Despite the fact that laws prohibiting the sale and misuse of cannabis exist and is considered a habit only entertained by lower-income groups, it is very rarely enforced. The occasional use of cannabis in community gatherings is broadly tolerated as a centuries old custom. The open use of cannabis by Sufis and Hindus as a means to induce euphoria has never been challenged by the state. Further, large tracts of cannabis grow unchecked in the wild Getty Where cannabis is and isn't legal Portugal In 2001, Portugal became the first country in the world to decriminalize the use of all drugs, and started treating drug users as sick people, instead of criminals. However, you can still be arrested or assigned mandatory rehab if you are caught several times in possession of drugs Getty Where cannabis is and isn't legal Puerto Rico Although the use of cannabis is currently illegal, it is said that Puerto Rico are in the process of decriminalising it RAUL ARBOLEDA/AFP/Getty Images Where cannabis is and isn't legal China Cannabis is grown in the wild and has been used to treat conditions such as gout and malaria. But, officially the substance is illegal to consume, possess and sell Getty

Expanding the federal "Compassionate Use Program" that once supplied marijuana to patients with a legitimate medical need. Currently, the federal government supplies marijuana to four patients in the U.S.

Simplifying the complex tangle of FDA licenses and regulations required to do marijuana research.

Ultimately, Hudak and Wallack point out that medical pot is a politically popular issue in the U.S., with upwards of 80 percent of Americans supporting the use of medical marijuana. "Medical marijuana reform should be an easy [issue] for a candidate seeking to connect with prospective voters and the expansion of medical research in the area should be an even easier consideration."

Hudak and Wallack see medical marijuana as a gateway drug to bipartisan cooperation in the next presidential administration. "Given public and congressional support for medical marijuana, the next president can use this issue as a springboard for overcoming gridlock in the early days of the new presidency," they conclude. It could be "a strong signal from a new president ready to turn a leaf on the dysfunction and distrust of the prior eight years."

Disclosure: The author of this story used to work at the Brookings Institution.