Generally in duty-free shops, anything delivered on a plane (such as duty-free alcohol) requires that you have a ticket for an international flight. They will scan the ticket and sometimes your passport.
@sandyf wrote:
Just heard from CXG about airport shops. They are for the International terminals but some airports are set up so that once you enter you can access all the terminals. Just be careful if it is a shop in an International terminal where you need to purchase something there are times when you can take your purchase with you and other restricted items from a duty-free shop where they deliver them on the plane. So if you are not flying you will never be able to get your purchase.
Shopping Southeast Pennsylvania, Delaware above the canal, and South Jersey since 2008