America's war on drugs seems to be in disarray, with federal and state laws governing the use of illicit substances increasingly at odds--especially when it comes to marijuana.

Federal law has long classified marijuana as a Schedule I controlled substance under the Controlled Substances Act, meaning the federal authorities have concluded that marijuana, along with other Schedule I drugs, meets three specific criteria: potential for abuse, no approved medical use, and a lack of accepted safety for use even under medical supervision.

Some state laws suggest marijuana doesn't meet that criteria. Under state laws, marijuana use has been permitted for sale as a prescribed remedy by 17 states and Washington, D.C., and a few states have decriminalized possession offenses for small amounts.

So, here lies the disaccord: "we’re moving toward a point where about a third of the population will be living in states where some medical use of marijuana is permitted even though it is still prohibited by the federal government," Dr. Sam Kamin, professor at the University of Denver's Sturm College of Law, told The Huffington Post. "That tension can’t go on."

That sums up what federal and state laws say about marijuana--but what does the science say? As you might expect, it's complicated. But here's how some leading experts and recent research help shed light on the drug and its place in U.S. laws:

  • Potential for abuse

With any substance of abuse there's a risk of addiction, Dr. Stefan G. Kertesz, associate professor at the University of Alabama at Birmingham School of Medicine, told The Huffington Post in an e-mail.

"Abuse is repeated use of a substance despite harm in your life, failure to fulfill major obligations, using the drug in dangerous situations, or using it in ways that cause relationship and legal problems," he said. "Does everyone who uses a drug wind up qualifying as 'abusing' or 'dependent' on that drug? No, but the risk is there."

Measuring how many people are addicted to a specific substance depends a lot on the method of study, he added. But research has shown that about 9 percent of people who use marijuana may become dependent, according to the National Institute on Drug Abuse. Meanwhile, about 32 percent of tobacco users become addicted and 15 percent of alcohol users, Psychology Today reported.

"The medical literature is clear--marijuana is absolutely addictive," Dr. Eric Voth, chairman of the Institute on Global Drug Policy and practicing internal medicine and pain medicine specialist, told The Huffington Post. "What makes it a little different is it’s a very long-acting substance… so if you compare it to cocaine or heroin those are drugs that if you stop you’ll very quickly have withdrawal symptoms. With marijuana you don’t undergo withdrawal so quickly."

  • Medical use

Marijuana is not an approved medicine under the Food and Drug Administration’s scientific review process, meaning the agency has found no scientific support for the drug's potential medical use. Interestingly, the FDA suggests that while smoked marijuana is not medicine, marinol has been legal and approved since 1985. Marinol contains synthetic THC in a capsule form, and often is used to relieve nausea and vomiting. The drug probably, possibly, maybe could be classified as "medical marijuana"—but let's not go there.

Many studies have shown that cannabis itself may benefit patients by helping manage pain, appetite and nausea—cannabinoids, such as THC, which are compounds derived from the cannabis plant, actually target those areas of the brain in control of such sensations.

Dr. Kertesz served as the senior author of a study published earlier this year in the Journal of the American Medical Association that found marijuana smoke to be not as damaging as cigarette smoke, and occasional marijuana use is actually associated with increases in lung capacity—a good thing.

"We think that likely is a result of how the way people smoke marijuana effectively trains them to do a bit better on the breathing test, practicing long breaths, holding it," Dr. Kertesz told The Huffington Post. "We don't agree with the surfers from Hawaii who think that smoking actually improves their ability to hold their breath under water."

  • Safety

In the U.S., there were 4.9 million drug-related emergency room visits in 2010, according to the Drug Abuse Warning Network. About 750,000 involved alcohol, while 461,028 involved marijuana.

A study published this year in the British Medical Journal found acute marijuana use was associated with an increased risk of a motor vehicle crash, especially for fatal collisions, Dr. Kertesz mentioned.

When looking at public safety, "there probably is a link between marijuana use and crime," Kamin said. "But it’s hard to see how much of that is attributable to the fact that marijuana is illegal."

He added that the consequence of marijuana’s prohibition turns it into a cash business, basically driving it underground, breeding that criminal element.

"There’s no question at all that with our laws as they are now marijuana is connected with crime," Rebecca Lonergan, a former federal prosecutor and associate professor at the University Of Southern California Gould School of Law, told The Huffington Post. "Because it’s the cartels who grow it, market it, make money off of it... The trafficking of marijuana is clearly linked with criminality, but it's chicken or the egg because if marijuana was not illegal would it be linked with crime? It's hard to say."

She said that marijuana's inflated cost possibly could motivate crime such as burglary or robbery--but she added such incidents are more commonly associated with "harder" drugs, such as crack and cocaine and methamphetamine.

The Arrestee Drug Abuse Monitoring report released in 2010 found that more than 40 percent of arrestees tested positive for marijuana.

  • Does it make sense to outlaw marijuana?

“I don’t have a strong position," Kamin said. "It’s clear that we spend a lot of money enforcing marijuana prohibition. We put a lot of people in jail, spending time, money and energy on policing, prosecuting, and imprisoning people. There’s probably a downside to marijuana legalization too. It might mean more people and kids use marijuana and some people might be using more serious drugs as a result... there can be other options, it doesn't have to be all or nothing."

To really answer that question--does it make sense to outlaw marijuana?--Lonergan suggested more research studying marijuana's risks compared to other Schedule I substances is needed.

"I wish that debate was still being a little bit interwoven with this and people were thinking about this a little more rationally and less emotionally," Lonergan said. "Is there some middle ground and compromise?"

HuffPost Live will be taking a comprehensive look at America’s failed war on drugs August 28th and September 4th from 12-4 p.m. ET and 6-10 p.m. ET. Click here to check it out -- and join the conversation.

Also on HuffPost:

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  • The Public Health Argument

    "Another legal drug, nicotine, kills more people than do alcohol and all illegal drugs -- combined. For decades, government has aggressively publicized the health risks of smoking and made it unfashionable, stigmatized, expensive and inconvenient. Yet 20 percent of every rising American generation becomes addicted to nicotine. So, suppose cocaine or heroin were legalized and marketed as cigarettes and alcohol are. And suppose the level of addiction were to replicate the 7 percent of adults suffering from alcohol abuse or dependency. That would be a public health disaster. As the late James Q. Wilson said, nicotine shortens life, cocaine debases it." -- <a href="http://www.washingtonpost.com/opinions/would-drug-legalization-do-more-harm-than-good/2012/04/04/gIQANg46vS_story.html" target="_hplink">George F. Will, Op-ed in <em>The Washington Post</em>.</a>

  • The Prison Population Argument

    "First, decriminalize possession of small amounts of any drug for personal use. That will have little impact on overall demand for illicit drugs, but it will significantly reduce the arrest and incarceration of millions of people worldwide, most of whom are poor and often members of vulnerable minority groups. It will also cut down on low-level corruption by police." -- <a href="http://www.nytimes.com/roomfordebate/2012/05/30/should-latin-america-end-the-war-on-drugs/regulate-drug-use-dont-criminalize-it" target="_hplink">Ethan Nadelmann, founder and executive director of the Drug Policy Alliance.</a>

  • The Economic Argument

    <a href="http://www.cato.org/publications/commentary/making-economic-case-legalizing-drugs" target="_hplink">A 2010 Cato institute study found: </a> "The report concludes that drug legalization would reduce government expenditure about $41.3 billion annually. Roughly $25.7 billion of this savings would accrue to state and local governments, and roughly $15.6 billion to the federal government. About $8.7 billion of the savings would result from legalization of marijuana, $20 billion from legalization of cocaine and heroin, and $12.6 billion from legalization of all other drugs. Legalization would also generate tax revenue of roughly $46.7 billion annually if drugs were taxed at rates comparable to those on alcohol and tobacco. About $8.7 billion of this revenue would result from legalization of marijuana, $32.6 billion from legalization of cocaine and heroin, and $5.5 billion from legalization of all other drugs."

  • The Economic Counter Argument

    "The tax revenue collected from alcohol pales in comparison to the costs associated with it. Federal excise taxes collected on alcohol in 2007 totaled around $9 billion; states collected around $5.5 billion. Taken together, this is less than 10 percent of the over $185 billion in alcohol-related costs from health care, lost productivity, and criminal justice. Tobacco also does not carry its economic weight when we tax it; each year we spend more than $200 billion on its social costs and collect only about $25 billion in taxes." -- <a href="http://www.whitehouse.gov/sites/default/files/ondcp/issues-content/directors_cal_chiefs_remarks.pdf" target="_hplink"> Gil Kerlikowske, director of the ONDCP (April 2010</a>)

  • The "It Works For Other Countries" Argument

    The report,<a href="http://www.release.org.uk/publications/drug-decriminalisation-policies-in-practice-across-the-globe" target="_hplink"> "A Quiet Revolution: Drug Decriminalization Policies in Practice across the Globe"</a>, finds that "countries and States as disparate as Belgium, Estonia, Australia, Mexico, Uruguay, the Netherlands and Portugal have adopted different models of decriminalization." Some countries (Spain and the Netherlands) have been moving towards decriminalization since the 1970s -- with the result that their drug use rates are lower than in the United States. -- <a href="http://www.huffingtonpost.com/ernest-drucker/decriminalization-of-drug_b_1656045.html" target="_hplink">Ernest Drucker, Huffington Post Blogger</a>

  • The "It Works For Other Countries" Counter Argument

    "For example, when The Netherlands liberalized their drug laws allowing the public sale of marijuana, they saw marijuana use among 18-25 years olds double, and the heroin addiction levels triple. They have since reversed this trend, and have begun implementing tighter drug controls. Indeed, today over 70 percent of Dutch municipalities have local zero-tolerance laws. Similarly, when the United Kingdom relaxed their drug laws to allow physicians to prescribe heroin to certain classes of addicts, they saw an entirely new class of youthful users emerge. According to social scientist James Q. Wilson, the British Government's experiment with controlled heroin distribution resulted in a minimum of a 30-fold increase in the number of addicts in 10 years." -- <a href="http://www.justice.gov/dea/demand/speakout/speak_out_101210.pdf" target="_hplink">Drug Enforcement Administration (2010)</a>

  • The Decrease In Crime Argument

    "[Legalization] does not take away everything [from the cartels], but it would reduce it. A large part of the extraordinary profits of drug lords come from the illegal nature of their business. If you remove the illegal nature, profits will drop. When profits drop, inevitably the violence will also decrease." -- <a href="http://www.hondurasweekly.com/mexico's-casta%C3%B1eda-calls-for-drug-legalization-in-us-201110264352/" target="_hplink">Jorge Castañeda, Former Foreign Minister of Mexico</a>

  • The "Legalization Will Not Reduce Crime" Counter Argument

    "What the legalization debate has missed is that it won't be easy for ex-criminals to find a legal job, and that this may increase other criminal activities that hurt Latin American citizens more directly. In places where law enforcement is weak, diversifying a criminal portfolio is an easier way to profit than trying to break into tight legal job markets. Indeed, it is quite plausible that legalization would cause newly unemployed criminals to engage in kidnapping, extortion, robbery and other forms of local crime. A criminal outburst may be the unintended consequence of legalization." -- <a href="http://www.nytimes.com/roomfordebate/2012/05/30/should-latin-america-end-the-war-on-drugs/drug-legalization-could-create-more-crime" target="_hplink">Viridiana Rios, Harvard Kennedy School doctoral fellow </a>

  • The Regulation Introduces Limited Safety Argument

    "Legalization does not mean giving up. It means regulation and control. By contrast, criminalization means prohibition. But we can't regulate what we prohibit, and drugs are too dangerous to remain unregulated." -- <a href="http://www.usnews.com/opinion/articles/2008/07/25/two-takes-drugs-are-too-dangerous-not-to-regulate--we-should-legalize-them" target="_hplink">Peter Moskos, John Jay College of Criminal Justice, in U.S. News and World Report</a>

  • The Regulation Has Its Limits Counter Argument

    There is no guarantee that the FDA would be able to regulate newly legalized drugs. The agency holds limited power to control alcohol and tobacco: "The Supreme Court enunciated the strongest arguments against the FDA's authority to regulate tobacco products in FDA v. Brown & Williamson : (1) the FDCA jurisdiction does not specifically include smoking products; (2) the legislative failure of proposed amendments extending FDCA jurisdiction to smoking products; and (3) Congress' enactment of separate "tobacco-specific" legislation. In 1996, the FDA issued a final rule in which it determined that nicotine was a drug and that cigarettes and smokeless tobacco are "drug-delivery devices." A group of tobacco manufacturers, retailers and advertisers filed suit in the Middle District of North Carolina against the FDA." -- <a href="http://leda.law.harvard.edu/leda/data/464/Kalam.html" target="_hplink">Murad Kalam, Harvard Law</a>

  • Colombian President Juan Manuel Santos's Show Me The Evidence Argument

    As the<a href="http://www.dailymail.co.uk/news/article-2061007/Colombia-president-Juan-Manuel-Santos-wants-rethink-Britains-cocaine-marijuana-ban.html" target="_hplink"> leading producer of cocaine in the world,</a> and the third most prolific source of marijuana, Colombia has faced drug cartel related violence for over half a century. The "success" of Plan Colombia, a joint U.S.-Colombia military and intelligence project that aimed to tamp down narcotics trafficking as well as the activities of left-wing insurgent groups in the South American country, has often served as an argument against legalization. However, the <a href="http://www.gao.gov/new.items/d0971.pdf" target="_hplink">United States Government Accountability Office (GAO) has deemed Plan Colombia only partially successful.</a> In April, Colombian President Juan Manuel Santos hosted the 2012 Summit of the Americas, where the drug war was considered a hot-button topic. Santos <a href="http://www.youtube.com/watch?v=lpr9HBf3ZOo" target="_hplink">said world leaders as a whole must first evaluate current initiatives before being able to find a permanent solution to the problem.</a> "If that means legalizing, and the world thinks that's the solution, I will welcome it," <a href="http://www.dailymail.co.uk/news/article-2061007/Colombia-president-Juan-Manuel-Santos-wants-rethink-Britains-cocaine-marijuana-ban.html" target="_hplink">Santos told the Daily Mail.</a> "I'm not against it."

  • President Barack Obama's "Legalization Is Not The Answer" Argument

    President Obama has acknowledged the United State's role in the drug war. "Unfortunately, the drug trade is integrated," Obama said during the Sixth Summit of the Americas in Cartagena de Indias, Colombia in April. "And we can't look at the issue of supply in Latin America without also looking at the issue of demand in the United States." Obama opposes legalization, opting instead to fight the demand in the U.S. through education and treatment for addicts. "We've invested ... about $30 billion in prevention programs, drug treatment programs looking at the drug issue not just from a law enforcement and interdiction issue, but also from a public health perspective. This is why we've worked in unprecedented fashion in cooperation with countries like Mexico on not just drugs coming north, but also guns and cash going south." --<a href="http://content.usatoday.com/communities/theoval/post/2012/04/obama-opposes-drug-legalization/1#.UDuFz2jyZ4U" target="_hplink">President Barack Obama at the 2012 Summit of the Americas</a>

  • Former Mexican President Felipe Calderón's Market Argument

    The former President of Mexico (2006 - 2012) declared a war against drug cartels that has been deemed unsuccessful by many who say it has prompted more violence. Calderón has often emphasized the need for the U.S. to take responsibility in the Drug War, frequently pointing out that the supply is fueled by <a href="http://articles.latimes.com/2010/oct/09/world/la-fg-mexico-calderon-prop19-20101009" target="_hplink">"the insatiable [U.S.] appetite for drugs."</a> Once fervently opposed to legalization <a href="http://articles.latimes.com/2010/oct/09/world/la-fg-mexico-calderon-prop19-20101009" target="_hplink">(speaking out against California's Proposition 19), </a> the former Mexican leader mentioned the need for<a href="http://latimesblogs.latimes.com/world_now/2011/09/mexican-president-drug-war-legalization-decriminlaization.html" target="_hplink"> "market alternatives"</a> as a solution for the drug war -- a statement many believe could mean legalization.

  • Guatemalan President Otto Perez Molina's Trapped In The Middle Argument

    Caught in the middle of the drug trade's flow from South America to the United States, Guatemala's homicide <a href="http://www.theblaze.com/stories/guatemala-president-to-propose-legalizing-drugs-in-central-america/" target="_hplink">rate of 41 murders per 100,000 people</a> has been attributed to the drug cartels by President Perez Molina. The violence in the country has prompted Perez Molina to advocate for legalization. "What I have done is put the issue back on the table,"<a href="http://www.cnn.com/2012/03/23/world/americas/guatemala-drug-legalization/index.html" target="_hplink"> Perez Molina told CNN en Español. </a>"I think it is important for us to have other alternatives. ... We have to talk about decriminalization of the production, the transit and, of course, the consumption."