Personally, I'll tell you up front I'm not a lawyer, however, I do not think there is a law to cover this other than proof has to be established prior to the election. If this isn't done, and Obammy is foreign born, or an Indonesian citizen, then the election is invalid period.
As to my knowledge, there is no precedent to follow on the what if. Nothing like this has ever been questioned.
There's more than a skeleton in the closet with this...it's a mass grave.