That's the sort of thing that becomes a question of fact for a jury. And as the the 6th Circuit said in
U.S. v. Burchard, 580 F.3d 341 (6th Cir., 2009) the Sixth Circuit found that (at 355):
would support conviction under 18 USC 922(g)(3).
So while it's a question of fact for a jury, there is guidance in regulation and case law as to how a jury is to decide whether someone is a "user." In law, we deal with those sorts of things all the time.
Or gun owners who might want to consider using marijuana, possibly medially, but want to keep their guns and avoid a length sojourn in federal prison.
But I actually suspect from your comment that you have nothing useful to contribute to this discussion. You might not take the law seriously, but at THR we help people understand the law, how it works and how it might apply. We do this so that we can help people make wise decisions and avoid violating the law. Getting caught violating the law can have very undesirable consequences.