I am not sure where Bennifer are considered residents, b/c they have homes all over the place, but........
In CA, LEGALLY [not morally], the person who got dumped keeps the ring. This also applies to other property [ie cars, homes etc] which was bought in preparation for the marriage, and only bought in reliance on the promise of impending nuptiuals [sp?].
To the dumpee go the spoils! However, if it was an heirloom ring, and it went to court, the dumper could argue for specific performance, and pay the appraised value of the ring to get it back.
I have heard that it was a mutual split, therefore they both hold on to all the extravagent gifts they exchanged.