Can My Employer Require That I Get My Doctor's Appointments Approved By Them First? [tennessee]

I have multiple physical and mental health issues that require me to see multiple doctors. I've had to reschedule appointments on the day of multiple times and eat the late fee with the next available appointment two months out. I do my best to work with my bossws to cause as little of an interuption as possible but they are still do not seem to be satisfied. We have a whiteboard in my department and part of it to dedicated to writing our time off. There is now a note on there on there saying any time off must be approved first. It doesn't explicitly mention doctors appointments or me by name but it was put there the same I came in one hour late because of an appointment. It implies that I need to get my appointments approved by them but doesn't outright state it. Is this legal and is there anything I can do about it?