Former president of the United States William Howard Taft is sworn in as 10th chief justice of the U.S. Supreme Court, becoming the only person ever to hold both offices.

The president of the United States (POTUS) is the head of state and head of government of the United States. The president directs the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.

William Howard Taft served as the 27th president of the United States from 1909 to 1913 and the tenth chief justice of the United States from 1921 to 1930. He is the only person to have held both offices.

The chief justice of the United States is the chief judge of the Supreme Court of the United States and is the highest-ranking officer of the U.S. federal judiciary. Article II, Section 2, Clause 2 of the U.S. Constitution grants plenary power to the president of the United States to nominate, and, with the advice and consent of the United States Senate, appoint "Judges of the Supreme Court", who serve until they die, resign, retire, or are impeached and convicted. The existence of a chief justice is only explicit in Article I, Section 3, Clause 6 which states that the chief justice shall preside over the impeachment trial of the president; this has occurred three times, for Andrew Johnson, Bill Clinton, and for Donald Trump's first impeachment.

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that turn on questions of U.S. constitutional or federal law. It also has original jurisdiction over a narrow range of cases, specifically "all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party." In 1803, the court asserted itself the power of judicial review, the ability to invalidate a statute for violating a provision of the Constitution via the landmark case Marbury v. Madison. It is also able to strike down presidential directives for violating either the Constitution or statutory law.