Do you have an employment contract or union agreement that prohibits such a change? Does this violate existing company policy? Is some for of actionable discrimination or retaliation a factor in your situation (you did not indicate this to be the case)? If not, then there really isn't much that you can do. The fact of the matter is that employers have a great deal of discretion setting the terms and conditions of the workplace. This includes who and when a person works a certain shift. In turn, employees can continue to work for their employer not. Additionally, employees can be fired for refusing to work their scheduled shifts. Actually, employees can be fired for any reason or no reason at all, with or without notice.