[TheAmazingIdiot]

Congratulations. You highlighted a misuse of the word license, and ignored the underlying idea that still is not answered.

"Where does the copyright exist at? Is it in the medium, the UPC, the box, or perhaps more intangible than that?"

Thought I was pretty clear I was not talking about a EULA or similar.

[unavoidable]

Then you have the reason why you haven't received an answer - your question is framed (almost deliberately) to have no answer. Copyright does not exist "in an object". It _is_ a state-enforced statutory right that "exists" in a "work" whether that work is a movie, music, software, book, etc. The "physical medium" you refer to is merely one copy of the "work" that is copyrighted. The work itself is necessarily incorporeal - it is an intellectual creation of somebody, and lies beyond the mere physical expression. You can do whatever you want with the box or medium - you are entitled to do that, except to the extent that you are limited by protection of the "work" that is copyrighted.

[TheAmazingIdiot]

Then how do you prove your copy is legitimately made copy from the rightsholder?

[SEMW]

You'd show it the same way you prove anything in a civil case: with evidence that, on the balance of probabilities, shows that it's the case. That's nothing to do with copyright law specifically.