Treason is "the highest of all crimes"—defined as intentionally betraying one's allegiance by levying war against the government or giving aid or comfort to its enemies. (In re Charge to Grand Jury, 2 Curt.C.C. 630 (D. Mass. Cir. Ct. 1851).) It's the most serious offense one can commit against the government and punishable by imprisonment and death. Treason prosecutions are rare, with around 40 federal prosecutions (and even fewer convictions) in U.S. history.
Treason is the only crime defined in the U.S. Constitution. According to Article III, Section 3:
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.
This section authorizes Congress to set the penalties for treason but not to change the definition or create degrees of treason. The federal treason statute, 18 U.S.C. § 2381, mirrors the Constitution's language and imposes minimum penalties of five years' imprisonment and a $10,000 fine. A conviction bars the defendant from holding any federal office and carries the possibility of the death penalty.
Most state constitutions include a treason provision similar to that in the U.S. Constitution. But state treason prosecutions are extremely rare—by most accounts, only three people have ever been charged with treason on the state level. This rarity is due to the fact that most treason threatens the nation, not merely one state.
Treason doesn't apply to foreign nationals who don't owe any allegiance to the United States. However, it does apply to American citizens holding dual citizenship. It also applies to aliens domiciled in the United States who owe a temporary allegiance to the country while living there.
The elements of treason are the same under state and federal law:
Because treason must be intentional, someone who unintentionally aids the enemy or is forced to by duress or coercion isn't guilty of treason. (See The Defense of Duress.) There can be no accomplice liability for treason; every participant is considered a principal.
There are two ways to commit treason: levying war against the government or providing aid or comfort to the enemy.
Levying war isn't limited to formally declaring war. It includes any forcible opposition to the execution of a public law. Such "forcible opposition" ordinarily requires actual use of force by multiple people with the common purpose of preventing some law from being enforced. Weapons aren't always required; sheer numbers can be enough.
Merely conspiring to overthrow the government isn't levying war—there must be an actual assemblage of people who are ready and intend to use force. (But see "Related Crimes," below.) So, no person acting alone can be guilty of levying war.
Providing aid or comfort to the enemy covers a variety of actions, from providing financial assistance to harboring an enemy soldier. Any intentional act that furthers the enemy's hostile designs or weakens the United States gives aid and comfort to, and "adheres to," the enemy.
Sympathy alone. Sympathy for the enemy by itself doesn't constitute aiding or comforting. Rather, the actor must take some kind of action to provide aid or comfort.
Time of war. Treason by aiding the enemy can't be committed during peacetime; there must be an actual enemy for the traitor to aid. The requisite enemy designation typically requires a formal declaration of war.
Attempt. Someone can be convicted of treason even if the attempt to aid isn't successful or the enemy's goal isn't achieved.
In order to prove treason, the prosecution needs either a confession or two witnesses testifying to the same "overt act" by the defendant. An overt act is an act that shows criminal intent and furthers the accomplishment of a crime. But, the overt act doesn't have to be a crime itself. A wide range of actions can qualify as overt treasonous acts, from making online posts to providing weapons and ammunition. The key consideration is whether the defendant took the action with the intention of carrying out or furthering treason.
Treason charges must specify the relevant overt acts, including where they took place. It isn't necessary that all the participants commit the same overt act; different participants can commit different overt acts as part of one treasonous plan. If the government alleges multiple overt acts, it need prove only one of them by two witnesses.
While testimony from two witnesses is required to prove the overt act, the intent to betray can be proved in the same way as intent for any other crime.
Treason is related and similar to several crimes. More than one criminal statute can apply to the same conduct, meaning that something falling short of treason may constitute another offense.
Sedition. Sedition (called seditious conspiracy in the law) involves conspiring to overthrow or destroy the government by force. Unlike treason, seditious conspiracy doesn't require that the defendant owe allegiance to the United States. (For more on conspiracy generally, see Conspiracy: Laws and Penalties.)
Insurrection or rebellion. Insurrection involves inciting, assisting, or engaging in an act of open resistance against the authority, laws, or operations of the government.
Misprision of treason. This crime involves someone knowing a person has committed an act of treason, failing to report it to a proper authority, and taking some action to conceal it. (For a detailed discussion of a related topic, see Misprision of Felony.)
Espionage. Espionage is obtaining classified information pertaining to national defense for use by a foreign nation. If the defendant aids a U.S. ally, treason can't be the charge, but espionage can. For instance, Ethel and Julius Rosenberg were charged with espionage rather than treason for trying to pass atomic secrets to the Soviet Union during World War II.
Terrorism. Treason and terrorism differ in that anyone (not just nationals) can commit the crime of terrorism and terrorism doesn't require that the United States be at war. (There are, however, similarities between treason and terrorism-related offenses—for instance, statutes criminalize providing material support to and harboring terrorists, among other actions.) To learn more, see Terrorist Threats.
Conspiracy to levy war. This precursor to treason doesn't require that people be assembled and ready to use force.