Took an A330 ftom Boston to JFK on a ferry. Passing 10,000 acars lights up with message to return to BOS as the CDG A330 was hard broke. Pull into the international terminal in BOS and customs says we have to clear customs. However they wont let us clear in since we never cleared out. Were it not for a customs supervisors with brain cells that actually communicated with each other we might still be there.