The verification could be on either end - maybe a packing & shipping service that verifies an item was packed (with photos, etc).

I would use this service. However, see my comment above. How would the Postal Service verify counterfeit merchandise, for example?

Gray market would be a ... gray area.

This took some work to find, but I found it:

https://www.amazon.com/gp/product/B00HT4BF4U

Its a control theory textbook for $44 from a 3rd party. Which is a pretty good deal because the "real" book sitting on my desk is somewhat more expensive.

https://www.amazon.com/Modern-Control-Systems-13th-Richard/d...

In very tiny letters the cover of the cheap version reads "Circulation of this edition outside the Indian Subcontinent is Unauthorized"

Something I find hilarious is the grey market edition is full of reviews that boil down to "this textbook sux and I hate my prof" but the genuine edition has one review by one guy who probably doesn't exist because if you click thru his reviews all look like stereotypical three word filler material.

They can't verify counterfeit merchandise but they could take a picture of the contents of the box and turn a device on to verify it works, like a pawn shop. There is no perfect way to solve this but the above solution would help.