You forget that in order to BE president, one must be a naturally born citizen. If he does not meet that, then he is not and has never been the president.
For the record, I actually believe that there's a reasonable chance that Barack Obama wasn't born in HI. I also believe that he likely took federal or state aid designed for foreign students. Which, is probably why he's so reluctant to release his college transcripts for Occidental, Columbia or Harvard.
As for "being President". Barack Obama IS POTUS. Regardless if he was born on the Moon to to space aliens, or actually born in HI to at least one or none US Citizens. He is now the sitting President. There's only one way to get rid of a sitting President. Impeachment in the House and Conviction in the Senate. That's not going to happen.
Even if overwhelming (and by overwhelming, I mean a home movie of Barry's mom giving birth) evidence came to light that he wasn't indeed born in the US, who exactly is going to hear that evidence. No court will, and no Senate or House sub-committee that's controlled by the Dems is going to convene hearing on the matter. And if they did, does that make him guilty of "High Crimes and Misdemeanors". Probably not. Has Obama ever sworn under penalty of purgery that he was born in the US? Again, probably not. I don't even recall him ever saying it aloud, much less affirming it in sworn testimony.
Effort and energy would be better spent fighting Obama on policy rather than litigating an "unlitigatable" fantasy.