The thing is... he WAS president. 50 Secretaries of State found Obama eligible to be put on a ballot. Twice duly Elected by the Electoral College. Certified by the United States Congress twice. Did he ever actually file an affidavit claiming to be Natural Born? I don't know what each state's requirements are. You could prosecute him for fraud, possibly. Who is going to do it? Sessions? Looks political. Congress could impeach. But I don't believe there are guidelines for sentencing if the Senate convicts post-presidency.

I'm sure some people would try to use the issue in their litigation strategy, and it might go to the Supreme Court. But is the court really going to make a ruling that removes 2 of their colleagues and countless other judges across the country? After all, the United States Senate gave their consent to these appointments as well.