Do Suspended Employees Have a Right to Lodge a Grievance?

Scenario: The employee was suspended with pay for alleged dishonesty. He then submitted solid proof that he had not been dishonest. After a further two months he had heard nothing from the employer, and lodged an internal grievance against the protracted, invalid and fruitless suspension. The employer refused to deal with the grievance and pointed him to its policy, signed by him, prohibiting the lodging of a grievance by an employee who has been subjected to a disciplinary process, in this case being the suspension. Was the employer legally correct to reject the grievance lodged?