Generally, it is unlawful for an employer to discriminate against an applicant based on national origin or race. However, citizenship is not a protected class of people under the relevant anti-discrimination statutes. That said, there are rules under the Immigration Reform Control Act (IRCA) that prevents discrimination on the basis of citizenship where the applicant has proper documentation of a right to work. However, there are some fairly broad exceptions, especially where the employment would place the employee into sensitive positions related to national security or law enforcement, to name a couple.
You should locate and consult with an experienced employment law attorney as soon as possible to explore your facts and determine your options. I would suggest you look either on this site in the Find a Lawyer section, or go to www.cela.org, the home page for the California Employment Lawyers Association, an organization whose members are dedicated to the representation of employees against their employers.
Good luck to you.
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