In Marbury v. Madison, decided in 1803, the Supreme Court, for the first time, struck down an act of Congress as unconstitutional. This decision created the doctrine of judicial review and set up the Supreme Court of the United States as chief interpreter of the Constitution. Judicial review is a process under which executive, legislative and administrative actions are subject to review by the judiciary.[1]: 79 A court with authority for judicial review may invalidate laws, acts and governmental actions that are incompatible with a higher authority: an executive decision may be invalidated for being unlawful or a statute may be invalidated for violating the terms of a constitution. Judicial review is one of the checks and balances in the separation of powers: the power of the judiciary to supervise the legislative and executive branches when the latter exceed their authority. The doctrine varies between jurisdictions, so the procedure and scope of judicial review may differ between and within countries