There have been quite a few judicial rulings that found Obama to be a natural born citizen. I can envision circumstances where courts could rule someone to not qualify as a natural born citizen which could set the stage for a state Secretary of State ruling that a candidate does not qualify for the ballot or a ruling could provide the grounds for the impeachment of an already elected official.
Courts that ruled Obama to be a natural born citizen.
1) Allen v. Obama (Arizona)
2) Ankeny v. Daniels (Indiana)
3) Fair v. Obama (Maryland)
4) Farrar v. Obama (Georgia)
5) Freeman v. Obama (Illinois)
6) Galasso v. Obama (New Jersey)
7) Jackson v. Obama (Illinois)
8) Jordan v. Obama (Washington)
9) Judd v. Obama (California)
10) Kesler v. Obama (Indiana)
11) Martin v. Obama (Illinois)
12) Paige v. Obama (Vermont)
13) Powell v. Obama (Georgia)
14) Purpura, et. al. v. Obama (New Jersey)
15) Strunk v. N.Y. Board of Elections (NY)
16) Swensson v. Obama (Georgia)
17) Taitz v. Obama [Quo Warranto]
18) Taitz v MS. Dem. Party & Obama (MS)
19) Tisdale v. Obama (Virginia)
20) Voeltz v. Obama, et. al. (Florida)
21) Welden v. Obama (Georgia)
If your list includes only state court cases, you have to keep in mind that it would be extremely gutsy for some superior court judge in some little county to try to disqualify a candidate for president so it is really hard to hold that against the folks who say he was unqualified. I doubt that a good lawyer would ever ask a state court to do something like that.