A person cannot serve as a member of a state legislature or hold federal office unless he or she?

Article 6 of the Constitution states, " The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution:"

In other Words, all officials, whether local state or federal, must take an oath to support and defend the laws stated in the United States Constitution.