Keeping it Legal
"What country are you from?" This question is clearly illegal because it discriminates against national origin. You can also get into trouble by asking an applicant what languages he or she speaks, unless speaking a certain language is part of the job description. There are exceptions, however. Suppose you are trying to hire a person for a job that requires a security clearance from the U.S. government. In this case, they must be a U.S. citizen. If you have included this requirement in your job description, then you may ask, "Based upon what I have told you, would you qualify for a security clearance from the U.S. government?"
Excerpted from Attracting & Rewarding Outstanding Employees