Ninth Circuit Court of Appeals Reorganization Act of 2003 - Divides the current U.S. Court of Appeals for the ninth circuit into: (1) the ninth circuit, composed of California and Nevada, consisting of 20 judges (25 as of February 1, 2005), and holding regular sessions in San Francisco and Los Angeles; (2) the tenth circuit, composed of Arizona, Colorado, Kansas, New Mexico, Oklahoma, Utah, and Wyoming, consisting of 14 judges (as of February 1, 2005), and holding regular sessions in Denver, Wichita, and Oklahoma City; and (3) the twelfth circuit, composed of Alaska, Guam, Hawaii, Idaho, Montana, Northern Mariana Islands, Oregon, and Washington, consisting of eight judges (ten as of February 1, 2005), and holding regular sessions in Portland and Seattle.Authorizes a circuit judge of the former ninth circuit who is in regular active service or who is a senior judge to elect to be assigned to: (1) either the new ninth or twelfth circuit; or (2) the new ninth or tenth circuit if such judge's official station is in Arizona.