“What we know from our decades of experience with medical marijuana is that the federal government has neither the resources, desire or ability to go after regular users.” With that thought in mind, you may find this interesting.

http://www.justice.gov/usao/eousa/foia_reading_room/usam/title9/27mcrm.htm

Go to 9-27.230, Initiating and Declining Charges—Substantial Federal Interest, Part B, Comment.