I've had a CCL on and off for years and been on the registry on and off since 2003. I've purchased two long guns and a handgun in that time. The feds are not checking the registry. AFAIK, they don't have the ability. I recall the CCW form is a state form. When you buy a gun, there's the blue federal form, but I don't recall it asking about marijuana. It's been two years, so it's possible I'm misremembering.