According to Arthur Herbert (see memo at right), Assistant Director of Enforcement Programs and Services at the ATF,
“any person who uses or is addicted to marijuana, regardless of whether his or her State has passed legislation authorizing marijuana use of medicinal purposes, is an unlawful user or addicted to a controlled substance, and is prohibited by Federal law from possessing firearms or ammunition”
and will be compelled to admit the prescribed use of medical marijuana on ATF forms at the point of purchase.
Feds: Medical Marijuana Patients Have No Right to Second Amendment
http://www.infowars.com/feds-medical-marijuana-patients-have-no-right-to-second-amendment/
And you thought Operation Fast and Furious was just a bunch of smoke...