If he was in NY for several days - did the gun materialize at the airport? Did someone with the legal right to have it - give it to him at the gate?
Is such a transfer legal?
I think he screwed himself for not understanding such.
That being said - I think it is a constitutional issue that you can be convicted of a felony for an action legal in so many states - that of being a law abiding citizen possessing a firearm. Unfortunately, Heller, etc. did not wash away all restrictions against law abiding citizens simply owning and transporting firearms.