It’s common knowledge that it’s illegal for US employers to ask about your age, sex, religion, marital status, national origin, or other protected statuses. Thing is, it’s not illegal for them to ask.  It’s illegal for them to discriminate, but it’s not illegal to ask. Still, the idea of the “illegal interview questions” is a common one. Search for “illegal interview questions” on Google and you’ll get 50,000 hits. Lots of blog posts and news articles, but nothing from anyone I see as a legal authority.

I’m certainly not a lawyer, but I feel confident in quoting the US Equal Employment Opportunity Commission’s website for this (emphasis mine):

As a general rule, the information obtained and requested through the pre-employment process should be limited to those essential for determining if a person is qualified for the job; whereas, information regarding race, sex, national origin, age, and religion are irrelevant in such determinations. Employers are explicitly prohibited from making pre-employment inquiries about disability. Although state and federal equal opportunity laws do not clearly forbid employers from making pre-employment inquiries that relate to, or disproportionately screen out members based on race, color, sex, national origin, religion, or age, such inquiries may be used as evidence of an employer's intent to discriminate unless the questions asked can be justified by some business purpose.

Short version: It’s not illegal to ask those questions, but it’s stupid to do so because it gives the candidate ammo to use in a lawsuit against you.

I think it’s an important distinction. I read plenty of comments on reddit and the like where people seem to think that being asked about their marital status is somehow going to get them a job because that’s an illegal question. It’s not. Other than feeding one’s sense of righteous indignation, there’s not much that will probably come out of being asked an “illegal question.” There has to be a lawsuit for anything to come of it, which means you need to find a lawyer who thinks that you can win a discrimination suit, because the lawyer will be able to prove discrimination.

The key is that you have to prove that you were discriminated against. Simply saying “They asked me an illegal question” isn’t enough. Here’s what a random employment law firm’s website says:

An employee in an employment discrimination and wrongful termination case must prove that the reason he or she was fired, or not hired or not promoted, is because of his or her “protected classification.” In other words, you have to prove that you were denied employment or a promotion because of your race, gender, ethnic background, age or other discriminatory factor.

It’s also important to know that in addition to the Federal laws, you may have rights in other states. For example, some states forbid discrimination based on sexual orientation, while many others do not (yet). Search Google for “discrimination laws [your state]” and you should get hits for your state’s government agency that covers this topic.

None of this is to endorse employers asking such questions. A good employer shouldn’t ask you any questions that aren’t related to the job.

What to do if you’re asked a question that gets at something discriminatory? Check out this article on how to handle bad interview questions.