If he hasn't already, I doubt he'll have any problems getting that rock back. If he lives in TX, good cause is needed and some pepper spray to the face and needing a restraining order I'd think would fit that criteria!
This looks to have taken place in CA and they have similar laws as TX with re to engagement rings....
"Sometimes Fault Matters
In states like
California, who gets the ring depends on who broke-off the engagement. So, if your fiancee calls off the wedding, she has to give the ring back to you. The same is true – in California, at least – if you both agree to call it off.
As a general rule, in states like this, you lose the ring if you cancel the engagement. An exception might come into play if you can show you had good reason to call off the engagement and so the cancellation was actually your fiancee’s fault. For instance, if you cancel the wedding after discovering your fiancee was unfaithful to you, a court may order her to return the ring."
