In Illinois "...In the absence of a contrary expression of intent, it is logical that engagement rings should be considered, by their very nature, conditional gifts given in contemplation of marriage. Once it is established the ring is an engagement ring, it is a conditional gift."
Kansas Heiman v. Parrish, 262 Kan. 926, 942 P.2d 631, 634 (1997) See, Illinois See Vann v. Vehrs, 260 Ill. App. 3d 648, 633 N.E.2d 102 (1994). Since the marriage was fulfilled, the gift is no longer conditional.
Other courts have reached a similar conclusion on the conditional gift concept.
California See Simonian v. Donoian, 96 Cal. App. 2d 259, 215 P.2d 119 (1950);
Connecticutt See White v. Finch, 3 Conn. Cir. Ct. 138, 209 A.2d 199 (1964);
Florida See Gill v. Shively, 320 So. 2d 415 (Fla. Dist. App. 1975);
Check with a lawyer in your locale to discuss more of the details. The law changes constantly.
Good luck to you.