As best I can determine, no one. It's an honor system. The applicant applies to be on the ballot in each state. Obviously no state demanded supporting evidence such as an original birth certificate.
However, at this point the Senate should be investigating. Diane Feinstein is head of the Committee with jurisdiction and no way is she going to start an investigation before the election.
If all the conservative talk show hosts made this topic of the day this week and we started calling and demanding that his eligibility be proven, God willing, we can stir the BS. Why hasn’t Hannity done anything on Fox???
Does that mean one of the secretaries of the states can demand the proof? FWIW,the Secretary of State for WV is a Republican who has no further plans for political office. It might be interesting if Obama was thrown off the ballot in a state. The media couldn’t ignore that.