Property

Most states treat an engagement ring as a gift conditioned on the marriage happening, so it goes back when the wedding does not, and a growing majority ignore who ended it.

Unmarried partners own what the paperwork says they own and owe what they signed for, because none of the sharing rules that come with marriage apply to them.

There is no divorce court for unmarried partners, so each shared asset and each joint debt has to be unwound separately under ordinary property and contract law.