A company fires an employee for campaigning for a candidate during her own time away from work. The employee files a civil case against the company. A judge rules that the company policy is unconstitutional. What power has the judge used?

The judge has used the power of judicial review, which allows the judiciary to review and interpret laws and government actions to determine their constitutionality. In this case, the judge has ruled that the company policy violating the employee's right to political expression is unconstitutional.