It appears, then, that in the United States two powerful forces are colliding over the issue of medicinal cannabis. On the one hand, there is a growing interest in and acceptance of the medicinal importance of cannabis, and there is every reason to believe that this development will continue to gain momentum. As it does so it increasingly confronts the proscription against any use of marijuana. At the same time, there does not appear to be widespread interest in moving from an absolute prohibition against cannabis to a regulatory system which would allow for the responsible use of this drug. The federal government, until recently has denied any medical utility to cannabis, and it appears to be vehemently opposed to any relaxation of the prohibition.
more at the link
I also noted Sativex was trying to position itself as "better" marijuana and has hired two former Bush Drug Czar officers to lobby for Sativex in the U.S.