Can employers change an employee's job duties, schedule or work location without his or her consent or prior notification?

Yes, in some cases. Generally, unless an employment contract or a collective bargaining agreement states otherwise, an employer may change an employee's job duties, schedule or work location without the employee's consent. In terms of notifications, some state and local predictive scheduling laws require businesses to provide workers with advance notice of their schedules or face penalties. In addition, when a schedule is changed upon the employee's arrival to work, and the employee's total hours of work that day have been reduced from what was known to be scheduled the prior day, some states have what are known as "reporting pay" or "show up pay" regulations that may require a minimum amount of hours to be paid to employees who have experienced a loss of hours that day. See Is 'On-Call' Scheduling on the Way Out? and Reporting Time Pay.

When an employee is on Family and Medical Leave Act (FMLA) leave, the act protects an employee's job duties, schedules and work location by prohibiting changes that include the following: changing the essential functions of the job in order to preclude the taking of leave; reducing hours available to work in order to avoid employee eligibility; transferring the employee to an alternative position in order to discourage the employee from taking leave; or otherwise placing a hardship on the employee. 

Upon returning from FMLA leave, employees must be reinstated to their job or an equivalent one. An equivalent position is one that is virtually identical to the employee's former position in terms of pay, benefits and working conditions, including privileges, perquisites and status. It must involve the same or substantially similar duties and responsibilities, which must entail substantially equivalent skill, effort, responsibility and authority. 

The employee is ordinarily entitled to return to the same shift, or a similar or equivalent work schedule. FMLA does not prohibit an employer from accommodating an employee's request to be restored to a different shift, schedule, position or location that better suits the employee's personal needs upon return from leave, or to offer a promotion to a better position. However, an employee cannot be induced by the employer to accept a different position against the employee's wishes.

In addition, schedule and duty changes made in retaliation for employees exercising their employment rights--such as filing a workers' compensation claim, taking FMLA leave, filing a wage or discrimination claim, whistle blowing, etc.--would violate the employee protections within those laws. And certainly, changes made based on unlawful discrimination (i.e., only women have their hours cut or authority reduced) would be unlawful.