The Court unanimously decided not to require Madison to deliver the commission to Marbury. Chief Justice Marshall understood the danger that this case posed to the power of the Supreme Court. Because Madison was President Jefferson’s secretary of state and Jefferson was head of the Democratic Party while Chief Justice Marshall and Marbury were Federalists, President Jefferson was almost certain to direct Madison to refuse to deliver the commission to Marbury. If the Court required Madison to deliver the commission and Madison refused, the Court had no power to force him to comply, and, therefore the Court would look weak. If the Court did not act, it would look like the justices made their decision out of the fear that Madison would not obey their decision. 

The justices struck a middle ground between these alternatives in their opinion, written by Chief Justice Marshall. The Court ruled that Marbury was entitled to his commission, but that according to the Constitution, the Court did not have the authority to require Madison to deliver the commission to Marbury in this case. They found that the Judiciary Act of 1789 conflicted with the Constitution because it gave the Supreme Court more authority than it was given under the Constitution. The dispute centered around the difference between the Supreme Court’s original jurisdiction and its appellate jurisdiction. If the Court has original jurisdiction over a case, it means that the case can go directly to the Supreme Court and the justices are the first ones to decide the case. If the Court has appellate jurisdiction, however, the case must first be argued and decided by judges in the lower courts. Only then can it be appealed to the Supreme Court, where the justices decide whether the rulings of the lower courts were correct. Marbury brought his lawsuit under the Court’s original jurisdiction, but the justices ruled that it would be an improper exercise of the Court’s original jurisdiction to issue the writ of mandamus in this case. 

The Judiciary Act of 1789 authorized the Supreme Court to “issue writs of mandamus … to persons holding office under the authority of the United States.” A writ of mandamus is a command by a superior court to a public official or lower court to perform a special duty. The Court said this law attempted to give the Court the authority to issue a writ of mandamus, an exercise of its original jurisdiction, to Secretary of State Madison. However, Article III, section 2, clause 2 of the Constitution, as the Court read it, authorizes the Supreme Court to exercise original jurisdiction only in cases involving “ambassadors, other public ministers and consuls, and those [cases] in which a state shall be a party. In all other cases, the Supreme Court shall have appellate jurisdiction.” The dispute between Marbury and Madison did not involve ambassadors, public ministers, consuls, or states. Therefore, according to the Constitution, the Supreme Court did not have the authority to exercise its original jurisdiction in this case. Thus the Judiciary Act of 1789 and the Constitution were in conflict with each other.

Declaring the Constitution “superior, paramount law,” the Supreme Court ruled that when ordinary laws conflict with the Constitution, they must be struck down. Furthermore, it is the job of judges, including the justices of the Supreme Court, to interpret laws and determine when they conflict with the Constitution. According to the Court, the Constitution gives the judicial branch the power to strike down laws passed by Congress, the legislative branch. This is the principle of judicial review. Thus, it has been recognized since this decision that it is “emphatically the province and duty of the judicial department to say what the law is.”

Through this decision, Chief Justice Marshall established the judicial branch as an equal partner with the executive and legislative branches within the developing system of government. By refusing to require Madison and Jefferson to deliver the commission to Marbury, he did not give Madison the opportunity to disobey the Court, making it look weak. And, by declaring the Court’s power through the principle of judicial review, he made it clear that the justices did not make their decision out of fear. Instead, he announced that the Constitution is the supreme law of the land, and established the Supreme Court as the final authority for interpreting it.