I can't fully recall which EU airport, but there was one, I believe it was BRU, that sealed their duty free. This allowed me to connect through LHR into the USA with the sealed duty free alcohol as hand carry. This would have been about 4-6 years ago.
Originally Posted by
MSPeconomist
Traditionally in USA airports, the duty free is delivered to the jetway so that you cannot give it to someone who uses it in the USA without paying excise tickets on it. I've never seen sealed bags (although I haven't really looked recently) like in EU airports, but it's common to staple the receipt to the bag so that the rightful owner gets all of the duty-free stuff that was purchased.