He's not. The Constitution is quite clear on this matter. Only impeachment in the House and Conviction in the Senate can remove a sitting President. That's not going to happen because a) The Dems handily control both Houses and b) So far, Barry hasn't committed a High Crime or misdemeanor (although, we did just start this show - anything is possible in the coming years).
The time to take care of this was before he was sworn. Either people couldn't or didn't. So, now we're stuck with him until 12:01 pm on Jan. 20, 2013.
“We”?
IF he’s not eligible, he’s not actually the President. You can only impeach someone who is actually the President. If he’s not eligible and lied and committed fraud, then he can be arrested, he’s not even eligible, in that case, to be impeached. Only actual Presidents can be impeached.