The classification of marijuana as a Schedule I substance remains a controversial topic.
Cannabis for medical use has been legalized in nearly half of the country, but it is illegal on the federal level. Here's why:
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The Controlled Substances Act was passed by the United States Congress, and signed into law in 1970.
Sparking debate: The push for medical marijuana legislation in Texas
The act established a federal U.S. drug policy under which certain substances are regulated. Those substances fall under five classifications or schedules.
Despite Congress initially passing the act, the classification of substances are determined only by the Drug Enforcement Administration and the Food and Drug Administration.
When it comes to the legalization of cannabis for medicinal purposes, the DEA has ruled that marijuana is a Schedule I drug, the highest classification possible, because the FDA has determined there is no current accepted medical use for marijuana in the U.S.
The FDA also considers marijuana to have a high potential for abuse, another key factor in Schedule I classification.
The FDA provides scientific data to the DEA, which in turn makes its scheduling judgments.
"At this point there have not been enough testing and research on marijuana that would put it in a category where it would be reduced to perhaps a Schedule II," said DEA special agent Dante Sorianello. "It needs to be supported by the scientific data."
The scheduling for marijuana does not appear to be changing anytime soon on the federal level.
The DEA announced in December that marijuana extracts, including cannabidiol or CBD, fall under Schedule I drug classification, making all forms of the plant illegal federally.
CBD occurs naturally in marijuana, and advocates argue it does not cause an individual high like THC.
Supporters say CBD has been proven to be a promising treatment for cancer patients and people with chronic pain, and it curbs the effects of epilepsy.
"It's incredibly frustrating for us as advocates because we can't reasonably explain why they are doing that," said Luis Nakamoto, executive director of National Organization for the Reform of Marijuana Laws. "Our own government has done studies and admitted that cannabis cures cancer, that cannabis helps with autism."
Despite those arguments, marijuana will remain a Schedule I substance for the foreseeable future, along with heroin and LSD, and above Schedule II drugs that include cocaine and methamphetamine.
"(It's) baffling us as advocates and patients because they are being treated as criminals. They are having to uproot their families from Texas, their home, and go to another state and be titled as medical refugees," said Nakamoto.
Below is an infographic and description of the current DEA's scheduling classifications from I to IV. (Click here if you can not view the graphic.)