What does this phrase mean: "s/he's an untouchable employee"?

This wasn't covered in my HR classes, and I have a feeling it has to do with the person's disability or other legally covered issues, but! there are people like that who are fired every day, so why would someone tell someone not to worry, they're untouchable? Just curious. I saw it in a skit I was watching to get ideas for my own. :D