Section 3 - The Text
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.
Section 3 - The Meaning
Treason is the only crime specifically defined in the Constitution. According to Article III, Section 3, a person is guilty of treason if he or she goes to war against the United States or gives “aid or comfort” to an enemy. He or she does not have to physically pick up a weapon and fight in combat against U.S. troops. Actively helping the enemy by passing along classified information or supplying weapons, for example, can lead to charges of treason.
Vocal opposition to a U.S. war effort through protest and demonstration, however, is protected by the free speech clause in the First Amendment. A conviction of treason must be based either on an admission of guilt in open court or on the testimony of two witnesses.
Congress may set the punishment, but it must be directed only at the guilty person and not at his or her friends or family if they were not involved in the crime.