This is borrowed from www.americanidol.com under Audition Rules:
You must be able to prove at the time of your audition, if any, that:
You are a legal U.S. citizen or a permanent U.S. resident who is eligible to work full-time in the United States; and
You are 16 to 28 years old on August 6, 2006 (which means you must be born on or between August 7, 1977, and August 6, 1990). If you were born before or after this window, you are not eligible to participate this season.
You are ineligible to participate if you progressed in any previous season of "American Idol" to any of the following levels:
Season 1 – top 30 contestants
Season 2 – top 32 contestants
Season 3 – top 32 contestants
Season 4 – top 44 contestants
Season 5 – top 44 contestants
If you are asked to audition for the semi-final rounds of the competition in the Los Angeles, California, area, you MUST be able to demonstrate (before departing for Los Angeles) that you do not have any of the following:
a contract for talent representation (for example, a talent agent or manager);
a music recording contract;
an acting and/or modeling contract;
a merchandising agreement; or,
any other contractual arrangement that would prohibit you from entering into an exclusive management contract, recording contract, talent contract, acting contract and/or merchandising contract.
You are ineligible if you, or any member of your immediate family and/or anyone living in your household, is an employee, officer, director, agent and/or representative of Fox Broadcasting Company, American Idol Productions, Inc., FremantleMedia North America, Inc., 19 TV Limited., CKX, Inc., Cingular, Telescope, Coca-Cola, the Ford Motor Company, Sony/BMG, production personnel for the television program, participating television stations, advertising agencies, corporate sponsors or any person or entity connected with the production, administration or judging of the auditions, or any of the parent companies, affiliates, subsidiaries, agents or representatives of any of the foregoing entities.