very true, however it is a bit moot now since the statuette of limitations has run out on all those bring backs so anyone caught with one can't be prosecuted...not that it's very easy to prove anyway since there are no definitive paper trails.
also a select few were allowed to take their rifles home. Alvin York was awarded his rifle when he returned home from WWI for instance.
"Bring back" is a term tossed about at gun shows to jack the price of a fire arm. Real bring backs had paper work like this.