Explain U.S Patent #6630507 in which The Dept of Health & Human Services holds the Patent for Medical Marijuana.

The Obama Administration just released a canned answer to the biggest petition on the We The People Petition site. It is claimed that Marijuana has no accepted medical use. Then why is a patent issued by the U.S Government on something that the Government says has no accepted medical use?

Here is the link to the US Patent Office:

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL...