The federal Immigration Reform and Control Act (IRCA) makes all U.S. employers responsible for verifying the identity and work. Other exceptions to "employment-at will" are in various laws.Federal and Arizona state laws stop an employers from firing an employee for a specific reason. Arizona law provides that an employer may terminate an employee at any time. The term is called "at-will employment." Information for Employers. An employer must withhold Arizona income tax from employees whose compensation is for services performed within Arizona. For more information, please contact your Secretary of State. Tackle complex global issues in a wide range of fulfilling career fields, from communication and sociology to history, economics, and beyond. Education.