Judicial Administration and Improvement Act of 2023 This bill divides the U.S. Court of Appeals for the Ninth Circuit into two judicial circuits: (1) the Ninth Circuit, and (2) a new Twelfth Circuit. The Ninth Circuit is composed of California, Guam, Hawaii, Oregon, Washington, and Northern Mariana Islands. The new Twelfth Circuit is composed of Alaska, Arizona, Idaho, Montana, and Nevada.