2 U.S. Code § 9
2 U.S. Code § 9 is about Voting for Representatives. It is under Chapter 1 (Election of Senators and Representatives) of Title 2 (The Congress) of the Code.
All votes for Representatives in Congress must be by written or printed ballot, or voting machine the use of which has been duly authorized by the State law; and all votes received or recorded contrary to this section shall be of no effect.