No, a "promise" ring is a gift, nothing more or less. A gift, once given, cannot be ungiven: it belongs to the recipient, not the giver, and the giver has no more right to it. While he could try filing a lawsuit (unfortunately, the courts don't prescreen lawsuits to make sure they are valid before accepting them), she should have a good defense based on the fact that this was a gift.Note: the above answer is based on it being only a "promise" ring and not an actual engagement ring and that your sister was not a fiance, engaged to be married. Actual engagement rings must be given back when the marriage is broken off, regardless of who broke it off, under CA law, such as California Civil Code § 1590.