Who has the authority to set the rules for elections? _Trailer

The Justice Department recently filed a lawsuit against the state of Arizona for passing a new law requiring voters to show proof of U.S. citizenship to vote in federal elections. This lawsuit goes to the heart of the matter: Who has the authority to set the rules for elections? The courts? The voter's representative? Or a government agency? ​​It just so happens that an important new case the Supreme Court will hear in October is about this very issue.