Since you don't have either an employment contract or union agreement to protect you in this situation, I'm afraid that you are out of luck. The fact is that most employment is "at will" which means that a company can set the terms and conditons of the workplace much as it seems fit short of acionable discrimination. This means that it can schedule an empoyee as necessary. Bottom line, you have no right to be laid off, so you can either quit or work the hours for which you have been scheduled.