The main purpose of this legislation, known as the Citizen Ballot Protection Act, is to allow states to require proof of citizenship from individuals who are registering to vote by mail. This amendment to the National Voter Registration Act of 1993 aims to enhance the integrity of the voter registration process by ensuring that only U.S. citizens can register to vote in federal elections. Key provisions of the law include the ability for states to add a requirement to their mail voter registration forms that applicants must provide evidence of their citizenship.