On the other hand, they do have the power to declare organizations terrorists. This is 8 USC 1182, thanks to the patriot act.
But he has not committed a crime in the US. Even if disseminating state secrets is a crime (and the jury's still out on that one, to boot) he didn't do it here.
He's going to pay a big price for his academic experiment. The US government has justifiably killed people over less serious attacks, and citizenship has nothing to do with it. And that's before you get to what has been done without justification (look up Ruby Ridge). When you pick a fight with a giant, you can expect to lose.
http://en.wikipedia.org/wiki/Church_committee
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The best they have on him are questionably well-timed sex crime charges.
And I'm fairly certain the law is fairly low on the CIA's radar of priorities.