Judicial review is the right of the Supreme Court to review laws made by Congress to ensure they are constitutional.
The policy of judicial review came out of the decision made in Marbury v. Madison. The case itself asked the Supreme Court to weigh in on the appointment of Marbury to a federal position. The Court proclaimed they had no right to push through an appointment but could review laws made by Congress. The Marshall Court used the opportunity to set the job of the Court.