This is in response to Second Carats. An engagement ring is given in contemplation of marriage, it represents a contract. When that contract is not fulfilled, no matter what the reason; the ring must go back to the groom (unless the bride paid for it). That is the law, the fact that this specific one belonged to his mother is irrelevant. Amy's advice was right on the money, your in the other hand will garantee this dumped girl a date with a judge.

Re: Ismael Rodriguez--I agree about returning the ring, because I can't imagine wanting to keep a ring that can't be worn, but I've never heard about any laws regarding this. I seem to recall Emily Post or Miss Manners saying that if the guy breaks the engagement, she gets to keep the ring if she wants. The guy would be better off giving her another ring if he wants the engagement ring back. Then good luck on getting another girl to take it. Most girls want a new one, not a second-hand one (family heirlooms notwithstanding). I somehow doubt this is on the legal books.

There are several schools of thought. The old fashion way is if the man breaks it off, the girl keeps the ring and if the girl breaks it off , she gives the ring back.
However, most judges and lawyers consider the ring a contract of marriage. If the marriage never happens, whoever gave the ring, gets the ring back (because of several cases of the woman fronting the money for the ring).
Amy made the right call about taking the high road. Do the right thing and give the ring back. Especially if it was a family heirloom.

The laws appear to vary from state to state. I still think if the guy breaks the engagement, it should be up to the woman, even though I personally would give the ring back. When my son broke his engagement, I tried to get him to let her keep the ring, and he was fine with it, but she insisted on making a big deal about returning it, despite the fact that she'd cheated on him. So, he hocked it for about a third of it's original price.
http://www.nolo.com/legal-encyclopedia/article-30198.html