The Constitution establishes a clear standard for eligibility that Obama likely did not meet. I don't see that there has to be a "nullification clause" to invalid his actions. The threat of a foreign born person with allegiances to groups/nations other than the US was precisely the reason for the provision.  I would think this is a matter to be litigated as it has never been tested in our history, just as the consitutionality of achor babies has never been tested but can be.