Is it illegal or immoral to put a spy camera in the restroom?

I am getting a new surveilance system and the salesman will not put a camera in the restoom, Yet I have found evidence of foul play while emptying the trash in that room, I dont mean aim it at the potty or anything like that. more the trash can, I have found remaiders of food and snacks I have for resale, and scratched off lottery tickets>? What is wrong with monitoring the trash>? I even had one use the restroom to spend half their shift on my telephone.