Judicial review is the power of courts to assess whether legislative and executive actions align with the constitutional framework. This process allows courts to invalidate laws or government actions that they find unconstitutional, serving as a crucial check on the balance of power among branches of government. Established in the U.S. by the landmark case Marbury v. Madison in 1803, judicial review ensures that the rule of law is maintained and protects individual rights from governmental overreach. It reinforces the principle of constitutionalism in governance.