I did it several years back, it is a bear, but it can be done
Stickslinger,
BLUF: It isn't easy, but it can be done. If you're active duty military, it might be easier, otherwise, be very, very patient. First, go ugly early and read the facts:
http://www.atf.gov/firearms/how-to/import-firearms-ammo-implements-of-war.html
Go ahead and contact ATF...after all, they are here to serve us law abiding citizens...especially on the "assumed C&R" question...
You have to complete an ATF-6...website and previous experience sez give yourself 4-6 months.
Mine was registered with USAREUR, so there was no problem de-registering it...however, yours may have to be deregistered by the country your FIL lives in.
You'll need to find a FFL with an import license...contact him first and he/she must be in the state of residence. Mine charged $50 for his services.
I was a DoD contractor in USAREUR and once all paperwork was legally sufficient and complete, was able to mail it via APO to the import FFL...labeled as "sporting good"s.
Import FFL handled the customs paperwork then shipped it to my local FFL. You'll have to pay the local FFL for his services and also for the NCIS check.
I shipped the greatest battle implement ever devised and ATF initially didn't want to allow it as it was a most deadly "implement of war", but I was able to get the State Dept to issue a ruling to ATF of no-concern....but to do that, I had to enlist the personal assistance of my US Senator (Ted Stevens) at the time...I don't know if Senators Warner or Webb would be willing...recommend contacting both via their local office in a nice letter asking for their assistance.
Good luck, it will take some time and lots of patience...recommend your FIL keep it secure IAW local laws. Under no circumstances should you (or he) try and beat the teacher and not follow the law...