Judicial review is significant in the U.S. legal system as it empowers the judiciary to invalidate legislation and executive actions that violate the Constitution. Established by the landmark case Marbury v. Madison, judicial review serves as a vital check on legislative and executive powers, ensuring that laws conform to constitutional principles. This process protects individual rights and maintains the balance of power among branches of government. Judicial review reinforces the rule of law by allowing courts to interpret the Constitution's meaning and safeguard against potential abuses of power.