Pumping in public?

Okay so this is mostly a question for those living in the us. Is there any law on using a beast pump in public?? I haven't been able to find anything saying I can't but yet there's nothing saying I'm protected if I do.... I'm mostly asking because in my line of work I usually end up sitting in waiting rooms with clients for hours on end and I will not pump ina bathroom (YUCK!). Also legally I can not leave my client to go to another room when out in the community (vulnerable adults) I've pumped in a waiting room once so far and it wasn't as bad as I thought it was going to be.. but I'm not entirely sure if I could be asked to leave if I do...

*also I do cover up if I have the right clothing to do so. It's cold in MN so I wear big sweaters that can accommodate the pump parts under it. During the summer I will buy a cover to use in this situation.

** and I can't usually put off pumping. I'm trying to maintain my supply so I so that have to suppliment while I'm away so I'm on a strict schedule

Thoughts? TA!