The potential argument is that these vehicles were imported under false pretense, and are retroactively illegal to import.

Very likely what will occur is that VW will force dealers to perform the recall with or without the owner’s consent.

Absolutely, the feds could very well put the car on a registration blacklist until the recall is verified as completed.

Being as this is a federal emissions issue, and not a state emission issue, owners might very well not be permitted to re-register their car without the recall being performed.