In Wisconsin, engagement rings are conditional gifts, and recovery can be made on the basis of unjust enrichment.[1]

In Brown v. Thomas, the court opined that the conditional gift theory is particularly appropriate when the contested property is an engagement ring.[2]  The court further observed that the inherent symbolism of the gift forecloses the need to establish an express condition that marriage will ensue.  The condition may be implied in fact or imposed by law in order to prevent unjust enrichment.

[1] Cantwell v. Hayward, 218 Wis. 2d 168 (Wis. Ct. App. 1998)

[2] Brown v. Thomas, 127 Wis. 2d 318 (Wis. Ct. App. 1985)