Judicial review is the power of courts to examine and invalidate laws or government actions that are found to violate the Constitution. This essential mechanism allows the judiciary to maintain a check on the legislative and executive branches, ensuring that laws and actions comply with constitutional principles. By doing so, judicial review plays a critical role in upholding civil rights and liberties, impacting various interpretations of the Constitution, the separation of governmental powers, and the enforcement of rights like those reflected in Miranda warnings.