What makes a law or action unconstitutional and does that determination ever change?

Download Primary Source Set: Judicial Review 

The courts play a unique role among the three branches in that the framers intended the courts to be insulated from public opinion in order to independently interpret the laws. Students begin their study of the work of the Court by reviewing in Marbury v. Madison (1803), to answer the question, What is judicial review and how does it work? Students concentrate on how the courts have interpreted the Bill of Rights over time, especially themes such as due process of law and equal protection as guaranteed by the Fourteenth Amendment, by answering the question, What makes a law or an action unconstitutional and does that determination ever change?