When The Engagement Is Over, Who Gets The Ring?

Gary here again pounding on the keyboard.  That picture above was Jana Kramer and me, long before she met Brantley Gilbert, but if you've been paying attention the last few days, Jana and Brantley Gilbert are now engaged. Brantley popped the question on his birthday and then presented her a 5-carat diamond ring.  Julie says this ring had to have cost tens of thousands of dollars and caused us to pause for a moment.  What if this relationship should ever go south?  Does she get to keep the ring?  Should she give it back?  According to my brother-in-law who's a Judge in Bossier and Webster parishes, the ring is consideration for a contract of marriage, sort of like a down payment.  If the marriage takes place, the contract is complete and the guy doesn't get the ring back.  However, if the marriage doesn't take place, the ring is returned.  Unless the ring was also a gift; Christmas or birthday.  Then it's more complicated.  But what about the ring after "marriage?"  What if the woman was adulterous?  Does she still keep the ring?  Should she give it back?  Thoughts?