The 1803 case Marbury v. Madison is one of the landmark decisions under John Marshall because it established the power of the judicial branch with the principle that the Supreme Court may declare an act of Congress void if it is inconsistent with the United States Constitution. This means the Court has the power to decide which laws are constitutional in what is known a judicial review.
Here is the history of this case:
The outgoing President, John Adams, who was anxious about losing positions from his political party, nominated forty-two judges prior to his leaving office so that his party's majority could out-rule the incoming President, Thomas Jefferson. One of the nominated judges was William Marbury.
When the last-minute commissions were not completely processed before Adams left office, Marbury was simply appointed as a judge. When Jefferson came into office, the judges' positions were reduced in number, leading Marbury to lose his job as part of this reduction. Marbury then submitted a grievance, asking the new Secretary of State, James Madison, to award him his position as justice of the peace for Washington County in the District of Columbia. When Madison denied Marbury his position in the court, Marbury subsequently petitioned for a writ of mandamus compelling delivery of the commissions.
Writing for a unanimous court, Chief Justice John Marshall thought that Secretary of State Madison was wrong for having denied Marbury his position; however, according to the U.S. Constitution, Marshall wrote, the Supreme Court did not have the power to issue such writs of mandamus.
Marshall determined that Section 13 of the Judiciary Act of 1789—authorizing the Supreme Court to issue writs to government officials—was unconstitutional because it was an extension of judiciary power into the realm of the executive.
Since the judiciary’s first responsibility is to uphold the Constitution at all times, Marshall wrote that if two laws conflict, the court bears responsibility for deciding which law applies in any given case. This decision in Marbury v. Madison, then, established what is known as judicial review. That is, the Supreme Court has the power to decide which laws are constitutional. In establishing judicial review, the decision of Marbury v. Madison has had a profound impact on American history.