The most significant result of the ruling in Marbury v. Madison (1803) was the establishment of the principle of judicial review. This meant that the U.S. Supreme Court gained the power to declare laws passed by Congress unconstitutional, thereby affirming the Court as the ultimate interpreter of the Constitution and a coequal branch of government alongside the legislative and executive branches

. Chief Justice John Marshall, writing the opinion, held that although William Marbury had a right to his commission, the Court could not issue a writ of mandamus to force delivery because the relevant section of the Judiciary Act of 1789 conflicted with the Constitution. By declaring that part of the Judiciary Act unconstitutional, the Court asserted its authority to invalidate laws that violate the Constitution, a power not explicitly stated in the Constitution but fundamental to maintaining the rule of law and checks and balances in the U.S. government

. This decision solidified the judiciary's role as an independent and coequal branch, capable of reviewing and limiting the actions of the other branches, ensuring that no law or executive act can supersede the Constitution. The precedent set by Marbury v. Madison has shaped American constitutional law and influenced landmark decisions ever since