Employees usually cannot refuse to work overtime hours. Employees who do refuse can get disciplined by their employer. This includes termination. There are some exceptions to this, though.
Your employer cannot fire you for refusing to work overtime if:
Working overtime breaches a contract
Working overtime affects your health and safety
You have a family emergency protected under the Family Medical Leave Act (FMLA)
You clocked 72 hours or more in the previous workweek
Employers are also required to modify an employee’s scheduled overtime if he or she is protected by the Rehabilitation Act or Americans with Disabilities Act (ADA).