The Supreme Court has upheld Arizona's use of independent commissions in drawing legislative districts. In order to prevent gerrymandering, the state elected, through public referendum, to establish an independent commission to draw congressional districts. The state legislature challenged this practice, arguing that it violated the constitution's Elections Clause, which declares that the time, place and manner of Congressional elections should be determined "in each State by the Legislature therefor," though Congress can alter those regulations.
The opinion, written by Justice Ginsburg and joined by Kennedy, Breyer, Sotomayor, and Kagan, held that states weren't limited to having their legislatures in charge of legislative districting, so long as the choice is enacted through proper means. "Legislature," read this way, isn't limited to elective representatives -- it means any law-making authority, including the people themselves.