I'd be inclined to just give the fella his rifle back. I'm guessing he is the one that bought it?
Can't transfer rifle to non-state resident without an FFL logging it and doing background check.
Then, I want you to find me an FFL that will transfer an AR to a New York resident.
I agree with MadMooner, however, the burden of transfer costs and legality belong to the ex-husband.
At this point, considering the guy is a jerk, he's likely to sic the ATF on her if she transfers the rifle in any fashion he can infer is questionable, if it belongs to her now because of any divorce paper clause.
