Marbury v. Madison, 5 U.S. (1 Cranch) 137 (1803), was a landmark U.S. Supreme Court case that established the principle of judicial review in the United States, meaning that American courts have the power to strike down laws, statutes, and some government actions that they find to violate the Constitution of the United States. Decided in 1803, "Marbury" remains the single most important decision in American constitutional law. The Court's landmark decision established that the U.S. Constitution is actual law, not just a statement of political principles and ideals, and helped define the boundary between the constitutionally separate executive and judicial branches of the federal government.