Further the ATF attempted to clarify any confusion with this memo that says "No Guns" if using marijuana, we don't care what the states allow."

http://www.atf.gov/press/releases/20...l-purposes.pdf

The CO medical MJ (and soon to be many other Colorado residents over 21 years ) users are lawful, per CO law.

It must be very confusing to someone filling out the form to say to themselves "Hmmm, are they asking about State or Federal law ?"
Yes, it is a Federal form, but I don't think most think that far ahead.

I would think that most MJ users would say "NO, I an not an UNLAWFUL user" , as they would honestly believe (not trying to lie) that since MJ is legal in CO, they are lawful, and have truthfully answered the question.

...or are firearms owners held to a higher standard than other citizens expected to know this distinction ?

What are firearm owners expected to do (legally) with their firearms and ammo if they wish to (legally) use marijuana * ?

Can they give "possession" of them to a friend, smoke a joint, and then go and retrieve them ?

After all, since they did not possess them while "using", and they are not currently "using" when they retrieved them, they didn't violate the letter of the law.

Does "possession" also mean "access to" ?
EX: Say my son lives with me and owns firearms and ammo. I use MJ and live in the same house. I do not own/possess them. Am I "OK" with the law?
Do I break the law if I touch one of them? or know the combo to the safe they are stored in?

*I know some of us might think, "Who's going to check? I'll just do it and keep my mouth shut." While this can be effective, I'm asking this from a legal perspective...
It comes down to the ATFs definition of what a "user" is ....(IMHO)