Job Making me change facial hair after they hired me?

Ok, I just started a job at papa john's and after they hired me with my hair the way it is the second day my manager told me I can't have a chinstrap style only mustaches and goatees, so nothing on the jaw line. Can they tell me that? how does that make a difference? It doesn't seem right that they could tell me the style, I thought only length, or no facial hair at all.