All full time retail workers are required to accept open availability as a requirement of full time status. In addition, most if not all retail workers are told right up front during orientation that holidays are black out dates, meaning, no vacation or day off requests will be accepted.
Retail is now the largest job sector in the US. So many of you suggest that if you don't like it, don't do it. Can't wait till you have kids or grand kids, and they come work for me, or company shills like me. Then you can talk your talk. Workers rights? No problem. We just ship those jobs out.
An at will employer can fire anyone for anything outside of protected classes, like sex, sexual orientation, or race, so long as the reason given wasn't present at the time of hire. In other words, you can fire an employee for getting their eye brow pierced, but not if they had one when you hired them.