The Constitution defines very few of its terms. The Congress has power to provide for uniform naturalization, but not to define "natural born" for Constitutional purposes, any more than they can redefine "arms" for purposes of the Second Amendment. There is no case law, as there has never been any challenge in courts to the eligibility of a Presidential candidate based on not being "natural born". There was only one other were it was even discussed, and he was Vice Presidential candidate who became President, Chester Arthur. In his case it was alleged, variously, that he was not born in the US and that his father was not a US Citizen at the time of his birth. From what I've read, it seems likely that the latter was true, but that the former was not. But AFAIK, no court ever examined the issue.
I'll agree insofar as no case I know of bears directly on Presidential qualifications, but the Court had plenty to say about "natural born" citizenship in US v. Wong Kim Ark, and NONE of what they had to say will give any comfort to the likes of trumandog and other Obama supporters.
If Wong Kim Ark, or indeed any prior case, is governing precedent or the dicta therein an accurate description of the law, then the Supreme Court needs to hear the case in order to clear the way for Obama's inauguration, for under the law as it stands unchallenged today, Obama cannot be legally sworn in.