Answer:
No. Generally, an employer has the power to dictate the employee's work schedule and hours. So if the employee refuses to work scheduled overtime, under most circumstances the employer may discipline an employee, up to and including termination.
However, there are exceptions -- an employee may validly refuse to work overtime if say for example, he is disabled and is asking for a reasonable accommodation or other similar circumstances where reasonable accommodation must be given to employees (pregnancy, religion, etc.).