I could see imposing US capital gains taxes, but barring travel to the US seems vindictive.
[edit] Also, how does it make sense to impose taxes AND bar them from entry? Seems like more of an either/or type of situation. If someone is paying US taxes, then obviously they should be allowed entry; no one wants to fund the mechanism that punishes them. [/edit]
He's a good politician, but a master self-promter. He focuses on hot issues to get cheap name recognition like the iPhone 4 "antennagate" issue, airport baggage fees, caffinated malt liquor and similar nonsense.