The 1803 Supreme Court case of Marbury v. Madison established the Supreme Court's power of judicial review (the power to declare acts of Congress unconstitutional). What did Marshall mean by the phrase "it is empathetically the province and duty of the judicial department to say what the law is"? Simple answer
Marshall meant that it is the responsibility of the judicial branch to interpret the Constitution and determine whether a law is in accordance with it, and to ultimately decide if the law is constitutional or not.
