His DL showed Colorado as his state of residence, right?
I mean my understanding is that you can sell/transfer a rifle to a person from a joining state but Texas and Colorado aren't jointing. Otherwise it has to be shipped to an FFL in the purchasers home state and transferred there. If there is an issue that got pass the shipping FFL concerning local laws it would be up to the Colorado FFL to reject the transfer to the Colorado resident/purchaser Right?
Did they change the joining state law while I wasn't looking?
You can purchase a rifle or shotgun, from an FFL, in any state as long as that purchase is legal in the state you are in, and your state of residence.
There are some states (FL is one that I happen to know because I live there) that have a law on the books that you can only purchase a rifle or shotgun out of state from an adjoining state, so to meet the "legal in both states" rule you need to be in an adjoining state. Those state laws are probably where you got that idea.
Texas and Colorado both allow relatively unrestricted rifle/shotgun purchases out of state, so the shooter was (or could have been) legal to by the rifle in Texas.
I'm not arguing that the sale was or wasn't legal. I just don't accept that "[It] doesn't matter what the FFL claims to have known."
I'm not arguing, I'm kinda feeling this whole thing out through discussion. I suspect that this little corner of law isn't actually very fleshed out. I said it doesn't matter what he claims to have known on the basis of most criminal law. If you do a straw purchase, and then claim as a defense that you didn't know it was illegal, they don't care. You're still guilty. Right? "Ignorance of the Law is no Excuse". Which then begs the question why right a line in the law that the FFL is assumed to know the laws of both states? Does it matter if he knows? It's still an unlawful transfer.
As far as I can tell that's what this case hinges on. If it was an unlawful transfer, then he has civil liability. If lawful, then he's protected from same.