Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.

The Congress shall have Power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.

The Constitution does not itself create the offense; it only restricts the definition (the first paragraph), permits Congress to create the offense, and restricts any punishment for treason to only the convicted (the second paragraph). The crime is prohibited by legislation passed by Congress. Therefore, the United States Code at 18 U.S.C. § 2381 states:

Whoever, owing allegiance to the United States, levies war against them or adheres to their enemies, giving them aid and comfort within the United States or elsewhere, is guilty of treason and shall suffer death, or shall be imprisoned not less than five years and fined under this title but not less than $10,000; and shall be incapable of holding any office under the United States.

The requirement of testimony of two witnesses was inherited from the British Treason Act 1695.