Is there something that proclaims ownership? For example if I'm married and if I don't want me wife being used by any and everyone can I file paperwork to make that happen? Or is that just allowed for the Elite?

In freeuse worlds societies, no, there is no such thing as “only I can fuck this person.” Even a house slut is free to be used by anyone who drops in.

In worlds of The Elite, it is only The Elite who can freely use anyone they like, unless they instruct someone to be used by anyone else.

Not all of my freeuse settings are the same world.