Is there a state law in FLA which prevents ineligible people from being on the ballot?
If the law allows it, one would seem to be arguing that such a law violates the constitutional (which sounds silly). It might be unconstitutional for Obama to take office, but unconstitutional for FLA to put him on the ballot?
Kick him off the ballot and that forces Obambi to become the plaintiff.
The states vary as to how they address this issue but in general have been far too lax. I don't know about Florida, but it seems anyone can run for anything and get away with it unless a challenge is put forth from the citizens or opponents, etc. This is opposite the way it should be. Challenges, and with them, the burden of proof, should be from those seeking placement upon the ballot. This way, the the eligibility issue would be legally addressed PRIOR to allowing someone on the ballot, whatever the office, especially the office of President.
If they won't do this they could pass a "Usurper Protection" Law which would require verification of compliance with the Twentieth Amendment, Section 3 before any signed legislation is obeyed by the state with such a law. This would make certain that Congress was doing its duty as well as protect that states citizens from the actions of a usurper. Since such a law would essentially be supporting enforcement of the Constitution, I don't see how it could be ruled unconstitutional.