Be careful. Complaining about an illegal question might cost you a job.

By law any question an employer asks should be directly related to ability to do the job. Marital status, ethnicity, age, affiliations and disabilities are only relevant if they directly hamper ability to fulfill job demands.

A candidate is free to answer any interview question: legal or illegal. Consider the intent behind the question. A question regarding native language, which is illegal, could be asked to determine ability to communicate clearly with coworkers and clients. A reply that indicates fluency in the required language would be appropriate.

Citizenship - Illegal - Are you a citizen?
Legal -Are you legally entitled to work in this country?

Marital status - Illegal - Are you married? Do you have children?
Legal - Are you able to relocate and work overtime?

Age - Illegal - How old are you?
Legal - Are you between the ages of 18 and 70?

Religion-- Illegal -What is your faith?
Legal - Do you require leaves of absence for religious observances?

Race - Illegal - What is your ethnic background?
Legal - None.

Handicap-- Illegal -Have you had any illnesses or surgeries?
Legal - Can you perform the essential duties of this job?

Affiliations - Illegal - What social groups and clubs do you belong to?
Legal - Do you belong to any professional associations or groups
relating to this job's functions?

Criminal Offenses - Illegal - Have you ever been arrested?
Legal - Employers may ask about criminal convictions on specific charges directly related to the job function,such as fraud in the case of a financial accountant.