If you are in possession of his rifle why don't you just give it to him (through a registered firearms dealer to cover your arse)...problem fixed.
The point is: So long as the ex lives in NY, the OP and his wifle can't legally transfer that rifle to him. The rifle is not registered, it's too late to register it and no FFL in NY can legally transfer it. The only way for the couple with the rifle to avoid legal jeopardy would be if the ex went to them and took the rifle back. Then when the ex transports it to NY, it is the ex that has the legal jeopardy, not the OP and his wife.
Now, don't shoot the messenger - again (Gitem 12 talking to you). I didn't make the law or support it, just letting the OP (and others here) aware of the very restrictive nature of the SAFE Act and trying to keep the OP and his wife out of any potential legal trouble they probably don't want.
