Ok, even if we assume that Obama was born in Kenya (which I don't believe), isn't it true he'd he still natural born citizen, because of his mother U.S. citizenship?
For example Lowell Weicker, when thought about 1980 presidential bid, asked his lawyers if the fact he was born in Paris makes him ineglible. They said no, because he was born to U.S. citizens.
What do you think?
A birthers arguement would be that he only had one American parent, instead of 2.
Irrelevant.
I am not so certain. It would depend on the US citizenship law at the time of his birth. If it awarded citizenship automatically at birth on the basis of one parent being a US citizen (so that only registering the fact of birth with US officials were required), that would make the point irrelevant. However, if it made one merely eligible to obtain citizenship on that basis using some sort of a "simplified naturalization" procedure (e.g., upon a parent declaration to a US consul) it could be relevant. The Constitution only clearly makes those born in the US citizens at birth (usually interpreted as satisfying the constitutional "natural born" provision). It does not preclude those not born in the US from being citizens at birth - but that's a matter of statute and statutory interpretation.
So, the right answer is: if he was born in the US he is a "natural born citizen" for sure, by Constitution. If he wasn't - it's a more complicated matter. Not that it makes him ineligible (in fact, most likely he'd be eligible anyway), but it would open legal avenues for questioning that.
