Who holds the power to appoint US Supreme Court justices?

Answer 1

The President, but he (or she) must have the consent of the Senate, which votes whether to accept or reject the nominee. If a simple majority (51% of those voting) affirms the President's choice, the nominee is appointed and becomes a US Supreme Court justice.

Answer 2

Congress

Congress can pass legislation that prevents the US Supreme Court from exercising appellate jurisdiction over certain Executive and Legislative actions, either in whole or in part. This is known as jurisdiction stripping, or curtailment of jurisdiction.

Congress cannot pass legislation that interferes with the Supreme Court's original jurisdiction, as granted by the constitution, nor can they concurrently remove jurisdiction from the Supreme Court and inferior courts, leaving no forum to challenge the legislation (although they may specify which court or courts will have original and appellate jurisdiction in such cases, as they did with Guantanamo detainees).

The power to assign jurisdiction derives from three constitutional sources:

Article I, Section 8, Clause 19

"...To constitute tribunals inferior to the Supreme Court;"

Article III, Section 1

The judicial Power of the United States, shall be vested in one supreme Court, and in such inferior courts as the Congress may from time to time ordain and establish.

Article III, Section 2

"...In all the other cases before mentioned, the Supreme Court shall have appellate jurisdiction, both as to law and fact, with such exceptions, and under such regulations as the Congress shall make."

Answer 3

the president