The Republican-controlled Legislature led by Senate President Andy Biggs and House Speaker Andy Tobin filed suit in federal court in June 2012.
They argued that the U.S. Constitution gives state Legislatures the right to regulate congressional elections and that voter-approved Proposition 106 in 2000 took that power away. The law created the Arizona Independent Redistricting Commission to draw district maps.
The three judges were appointed Monday by Alex Kozinsky, chief judge of the 9th U.S. Circuit Court of Appeals. They are Senior Circuit Judge Mary Schroeder and District Judges Paul Rosenblatt and Murray Snow.
Another three-judge panel is weighing a separate challenge to legislative district boundaries adopted by the commission in January 2012.