The Biden defamation thing would be an argument against prosecution as KR could argue Biden’s comments were so prejudicial as to preclude him from receiving a fair trial.
Plus I think it would backfire badly on Biden both personally, making him appear even more petty and partisan and politically in terms of further dividing Americans.
You're drawing a line that isn't in the statute. Why isn't it a transfer when I simply hand it to you? That's certainly enough "possession" for a violation of 922(g). (922(d) clearly requires dispositional transfers). You could argue that we're in joint possession, so no transfer, but the same argument could be made for Dominick Black. If he still exercised some amount of dominion and control, then he was still in constructive possession throughout the night.
What if I housesit for you and you have unsecured firearms that I have knowledge of? Does a violation of 922(a)(5) occur? Assume we're residents of different states obviously.
Not to mention you can't sue POTUS.....so @WDR's idea of Biden pressuring the DOJ to prosecute him in response to KR suing Biden for defamation/libel is a non-starter anyway.
"Are you ready? Okay. Let's roll."- Last words of Todd Beamer
So, I don't think I'm qualified to converse legal theory with you. I'm looking at it from my perspective as a LEO.....and, to reference @HCM's comment about a bright line, let's say for the purposes of example that you're a felon just because it makes it easier to visualize:
Situation A: I find you outside and you have your friend's gun on you; I'm automatically adding the charge.
Situation B: I find you inside your friend's home, and unsecured guns are present; you might be getting the charge based on some specifics that are lacking from this example, but I'm probably calling the AUSA first.
At some point somebody actually has to do something instead of argue legal theory, which is why we have this rules of thumb/"bright line" as HCM put it. You very well might be right and have some compelling argument in theory, but on the street you're getting the gun charge. If you weren't a felon and were just house sitting and guns that belonged to the owner/tenant were in the house, I don't see how that would be considered a transfer of possession under federal law since they're still in the owner's dwelling. Griffin might be a good case to review about that.
"Are you ready? Okay. Let's roll."- Last words of Todd Beamer
Both situations A and B have been sustained under 922(g) as far as I know. But, I'm talking about 922(a)(5).
As you point out, you don't think this would be a transfer for nonprohibited persons, which is kind of my point. 922(a)(5) clearly isn't strictly applied according to its text.
Also, Kyle's dad is a resident of Wisconsin. There's certainly an argument that Kyle was a resident of both states under 27 CFR 478.11.
I also just realized that 922(a)(5) does not require that the firearm is "shipped or transported in interstate or foreign commerce." If it were applied to a purely intrastate transfer of a firearm, it could be constitutionally defective under United States v. Lopez.
"Are you ready? Okay. Let's roll."- Last words of Todd Beamer