Ok, I was thinking this was possible but for some reason it doesn't work. I've set the following rule condition on a validation rule for a people control. Essentially I want to require this control from being empty.
Approver is the name of control. It does not matter if I have data in there or not, the control is never invalidated. Now, I've only been testing via preview. Is there some sort of bug that prevents this from working that I missed somewhere?