Employer Asking For Letter Of Explanation For Arrest, But Background Check Came Back Clear

Hello,

A potential employer I’ve been in contact with recently ran a background check on me, which they said came back clear. About a week or two later, they reached out to me again to let me know that, while the background check did come back clear, “information not contained in the background check has come to our attention that raises the possibility that there may be one or more criminal convictions that would make you ineligible for employment.”

To be transparent, I was arrested 10 years or so ago for possession of an illegal substance (marijuana). I did probation which just entailed a drug test once a month for about a year, and that was the end of it. I was told that it wouldn’t be something that would show up on my record, and previous employers that ran background checks never said anything about it and seemingly never knew about it.

There was another arrest around the same time for a domestic violence incident, however the charges were dropped within 24 hours once the investigation concluded and it was found that I acted in self-defense. I was just let go and nothing came of it.

With that said, with this employer stating my background check is clear, am I still obligated to disclose information not contained in it to them? Is that legal on their end to deny me employment when said background check is clear? What even is “more information” and are they allowed to use this against me?

This is all new to me. Like I said, no previous employer even mentioned it or seem to know about it. I would really appreciate anyone’s advice. I feel hopeless. Thank you.