Buying a firearm and having a Medical Marijuana card?

[stanc]

On the ATF form 4743 it asks if your addicted to marijuana etc..? What happens if you've got a MM card and the ATF sees it on a background check? See where I'm going? I heard from a guy in Michigan that said you can't buy a firearm if you have a medical marijuana card. .
Why doesn't the form ask if your a alcoholic? DUI?

Undoubtedly because consumption of alcoholic beverages is not in violation of Federal law.

If Prohibition had not been repealed, and alcohol use was made legal at the State level, it's a safe bet that such a question would be on the 4473.