Where can I find info on employee/er rights regarding firing based upon odor?

I have been igned a panel discussion project for my behavior and diversity cl. Our position is that employees should not be fired based upon tattoos, attractiveness, or odor. I have spun my wheels from the ADA site to HR newsletter sites and it appears our position is very weak. Does anyone have links or sites that could be of help? Suggestions are very welcome. Thanks!