In Minnesota, an engagement ring is a conditional gift, given in contemplation of marriage.  The state courts have held that marriage is an implied condition of the transfer of title to the ring, and the gift does not become absolute until the marriage occurs.[1]  When two parties engaged to be married decide to abandon their plans for future marriage, the engagement ring shall be returned to the donor regardless of fault.

[1] Benassi v. Back & Neck Pain Clinic, Inc., 629 N.W.2d 475 (Minn. Ct. App. 2001)