Hamilton had always regarded the judiciary as the final fortress of liberty and the most vulnerable branch of government. John Marshall remedied that deficiency, and many of the great Supreme Court decisions he handed down were based on concepts articulated by Hamilton. In writing the decision in Marbury v. Madison (1803), Marshall established the principle of judicial review--the court's authority to declare acts of Congress unconstitutional--drawing liberally on Hamilton's Federalist number 78. His decision in the landmark case of McCulloch v. Maryland (1819) owed a great deal to the doctrine of implied powers spelled out by Hamilton in his 1791 opinion on the legality of a central bank.