Nominating a non-art object as an artwork requires that the object not be an art object. But imagine that you have a time machine. Now you can go back in time to ancient Rome or Greece with any non-art object that you wish to nominate as an artwork and have it accepted as a work of art. Not declared; displayed and accepted.
Assuming you avoid temporal paradoxes, the object will never have been a non-art object and so will not now need nomination. Is this just nomination at an extra level of indirection, or does it undo the readymade?
That IS the temporal paradox!
“Not now need nomination”? Art continously needs renomination as art. If I go back in time and “make it art,” I can still reappropriate it as art later, almost as if it wasn’t art in the first place. Like Lichtenstein.