I just came back from a one week vacation. My first day back, My position as mens merchandise manager had been given to another associate and I was given a position as merch. manager of domestics. Is this legal without notifying me first?

I just came back from a one week vacation. My first day back, My position as mens merchandise manager had been given to another associate and I was given a position as merch. manager of domestics. Is this legal without notifying me first?