Marijuana is the only major drug of abuse grown within the U.S. borders and for that reason the US Drug Enforcement Agency, which has a nationwide law enforcement program that targets drug trafficking organizations involved in cannabis cultivation, was unlikely to change its mind on reclassifying marijuana as "medical" just because some states did.
In truth, there is no drug that helps the variety of issues (everything from glaucoma to epilepsy) marijuana proponents claim it does. It is anecdotal evidence and the placebo effect and, in a lot of cases, people getting a card for "pain" just so they can legally smoke it. DEA affirms that marijuana has "no currently accepted medical use and a high potential for abuse," and will keep it a Schedule I drug under the Controlled Substances Act (CSA), with cocaine and heroin, after a scientific and medical evaluation conducted by the US Food and Drug Administration found no new evidence it can be medicinal.
There is good news for science, though. It may be that marijuana hasn't yet found a medical benefit because it is so hard to get approval to study.
Currently only the University of Mississippi has a license to grow it for research, making it difficult to do well-controlled clinical trials. DEA has stated they will start licensing additional suppliers of marijuana so that marijuana can (or can't) begin to survive clinical trials.
