Schedule I of the CSA specifically states that in order to be placed in this schedule I that the substance in question must have "no accepted medical use for treatment in the United States." Well, as of 1996 there were states that have accepted the medicinal uses of marijuana for treatment, yet there was no reclassification.
In 1988, when Administrative Law Judge Francis Young ruled that the DEA was required to reclassify marijuana there again were no states that had accepted the use for treatment and therefore the DEA had due cause to ignore the recommendation.
Now 2013, 18 states have ACCEPTED medicinal uses for marijuana, therefore the current scheduling goes against the definition that was put into place and marijuana should be reclassified immediately.