I don't know if that's universally true in the US. Most labor laws such as these are set on a state (and sometimes local) level, so it's kind of a hodge-podge. For example, in Louisiana it's still legal to discriminate on the basis of sexuality, but not age, race, gender, or disability. But then in Orleans Parish (parishes are counties in Louisiana) it's not legal to discriminate on the basis of sexuality.

I'm not a lawyer though, and I have no idea what the federal law says regarding arrest vs conviction records. I do know that I've filled out numerous employment applications in many states that required me to disclose convictions of misdemeanor or worse crimes, but never any that have asked about an arrest record.