The U.S. Government holds a patent on its use because of its medicinal properties. Please see Patent # US 6630507 - Cannabinoids as antioxidants and neuroprotectants. You can read the entire patent at:
http://www.google.com/patents/US6630507
Removing marijuana from the Controlled Substances act or at the very least re-scheduling it, would allow millions of Americans who are currently prevented from using medical marijuana without fear of prosecution to benefit from its therapeutic value. By removing marijuana from Schedule I and legalizing its use as a medicine in the U.S. the huge increase in tax revenues that would be generated through taxation on the sales of marijuana could be spent on medical research and healthcare.