Section 2331 of Title 18 of the U.S. Code is the federal statute that defines “domestic terrorism” and “international terrorism.” It does not criminalize anything on its own. Instead, 18 U.S.C. 2331 supplies the vocabulary that dozens of other federal laws use when they impose penalties, authorize investigations, freeze assets, or let victims sue. Whether a case is classified under one definition or the other decides which tools prosecutors can reach for, what sentence a defendant faces, and whether victims have a federal cause of action.1Office of the Law Revision Counsel. 18 U.S.C. 2331 – Definitions
What Section 2331 Actually Does
Section 2331 is purely definitional. It tells prosecutors, courts, and agencies what “terrorism” means whenever the word appears elsewhere in Title 18 and related statutes. No one is ever charged with a violation of 2331 itself.
The FBI, the Department of Homeland Security, and the Department of Justice rely on these definitions to classify threats and decide which investigative authorities apply. The same definitions drive material support prosecutions under 18 U.S.C. 2339A and 2339B, civil forfeiture under 18 U.S.C. 981, and civil suits by victims under 18 U.S.C. 2333. The USA PATRIOT Act of 2001 leaned on these definitions when it expanded federal investigative powers.
How the Statute Defines Domestic Terrorism
Under 18 U.S.C. 2331(5), conduct qualifies as domestic terrorism only when three elements are all present:1Office of the Law Revision Counsel. 18 U.S.C. 2331 – Definitions
- Acts dangerous to human life that violate federal or state criminal law.
- Conduct that appears intended to intimidate or coerce civilians, influence government policy through intimidation, or affect government conduct through mass destruction, assassination, or kidnapping.
- Activity occurring primarily inside U.S. territory.
A violent crime without a political or coercive motive is not domestic terrorism. Politically motivated activity that is not dangerous to human life is not either. The FBI has described the line as the point where someone crosses from exercising First Amendment rights into committing crimes in pursuit of violent goals, and says its investigations focus on unlawful activity rather than ideology.2Federal Bureau of Investigation. Terrorism
The single most important practical fact about this definition: there is no standalone federal charge called “domestic terrorism.” The label exists for classification, but prosecutors cannot use it as a count in an indictment. People who commit acts fitting the definition are charged under whatever specific statutes their conduct violates — explosives offenses under 18 U.S.C. 844, material support under 2339A, firearms crimes, or hate crime statutes, among others.
The gap runs further. There is no mechanism to formally designate a domestic group as a terrorist organization, so the asset-freezing and immigration tools available against foreign terrorist organizations do not reach purely domestic extremist groups. Whether Congress should create a domestic terrorism charge or a domestic designation process is an active policy debate.
How the Statute Defines International Terrorism
Under 18 U.S.C. 2331(1), international terrorism has three parallel requirements:1Office of the Law Revision Counsel. 18 U.S.C. 2331 – Definitions
- Violent acts or acts dangerous to human life that violate federal or state criminal law, or that would be criminal if committed within U.S. jurisdiction.
- The same coercive-intent element as the domestic definition.
- Conduct occurring primarily outside U.S. territory, or crossing national borders in how it is carried out, who it targets, or where the perpetrators operate or seek asylum.
The intent element is the same as in the domestic definition. The differences sit in scope. The international definition covers “violent acts or acts dangerous to human life,” slightly broader than the domestic wording. It also reaches conduct that “would be a criminal violation if committed within the jurisdiction of the United States,” which lets the government classify foreign acts as terrorism even when they occurred where local law differs from U.S. criminal law.
The third element matters most in mixed cases. An act carried out inside the United States can still be classified as international terrorism when it crosses national boundaries in planning, execution, targeting, or the perpetrators’ movement. Classification as international rather than domestic unlocks a suite of tools the domestic label does not, including civil suits for treble damages and the full weight of the foreign terrorist organization designation system.
Why the Difference Matters
Three practical consequences follow from which side of the 2331 line a case falls on.
First, only international terrorism connects to the Foreign Terrorist Organization designation system. Under 8 U.S.C. 1189, the Secretary of State can designate a foreign group engaged in terrorism as an FTO. Once designated, financial institutions must freeze the group’s U.S.-held assets, providing knowing material support becomes a federal crime under 18 U.S.C. 2339B, and members can be denied entry or removed under immigration law. The designation cannot be challenged as a defense in a criminal prosecution: arguing at trial that the group should never have been listed is not an available defense.3Office of the Law Revision Counsel. 8 U.S.C. 1189 – Designation of Foreign Terrorist Organizations
Second, only international terrorism gives victims a federal right to sue (covered below). Victims of an act classified only as domestic terrorism do not have access to the 2333 cause of action.
Third, both definitions feed the sentencing consequences discussed later in this article, but they do so through the specific federal offenses charged. The classification alone changes what investigative and post-conviction tools are on the table.
The Charges 2331 Unlocks
Two statutes drive most terrorism prosecutions, and the definitions in 2331 sit behind both.
18 U.S.C. 2339A makes it a crime to provide material support knowing it will be used to carry out specific violent offenses listed in the statute. The penalty is up to 15 years, or any term of years up to life if a death results.4Office of the Law Revision Counsel. 18 U.S.C. 2339A – Providing Material Support to Terrorists
18 U.S.C. 2339B targets support to designated FTOs. Prosecutors do not have to show the defendant knew how the support would be used; they need only show that the defendant knew the organization was designated or engaged in terrorism. The penalty is up to 20 years, or life if a death results.5Office of the Law Revision Counsel. 18 U.S.C. 2339B – Providing Material Support or Resources to Designated Foreign Terrorist Organizations
“Material support” is defined broadly. It covers money, property, services, lodging, training, expert advice, weapons, explosives, false documents, communications equipment, transportation, and personnel. The statute explicitly excludes only medicine and religious materials.6Office of the Law Revision Counsel. 18 U.S.C. 2339A – Providing Material Support to Terrorists
The breadth of the term has been tested at the Supreme Court. In Holder v. Humanitarian Law Project (2010), the Court upheld the government’s authority to prosecute people who provided training in peaceful conflict resolution to designated groups. The majority reasoned that even nonviolent assistance can be criminal because any support frees up an FTO’s own resources for violence.7Justia U.S. Supreme Court Center. Holder v. Humanitarian Law Project, 561 U.S. 1 (2010)
Civil Lawsuits by Victims
Under 18 U.S.C. 2333, any U.S. national injured in person, property, or business by an act of international terrorism can sue in federal district court. The victim’s estate, survivors, and heirs also have standing.8Office of the Law Revision Counsel. 18 U.S.C. 2333 – Civil Remedies
A successful plaintiff recovers three times actual damages, plus costs and attorney’s fees. Liability reaches beyond direct perpetrators: anyone who knowingly provides substantial assistance to someone who committed an act of international terrorism planned or authorized by a designated FTO can be held liable. A criminal conviction in a related federal case also estops the defendant from denying the core facts in a follow-on civil suit, and judgments can be satisfied out of blocked assets seized under terrorism-related sanctions.
The 2333 remedy is tied to the international terrorism definition. Victims of conduct classified only as domestic terrorism do not have this federal cause of action.
Sentencing Consequences When Terrorism Applies
Once a defendant is charged under a statute that qualifies as a “federal crime of terrorism,” the sentencing consequences compound.
The Terrorism Enhancement
U.S. Sentencing Guidelines §3A1.4 raises a defendant’s offense level by 12 when a felony was intended to promote a federal crime of terrorism, with a floor of level 32, and automatically places the defendant in Criminal History Category VI, the highest possible.9United States Sentencing Commission. U.S. Sentencing Guidelines Manual – 3A1.4 Terrorism The combination often produces a guidelines range calling for life imprisonment even where the underlying offense would otherwise carry a much shorter sentence. The qualifying offenses are listed in 18 U.S.C. 2332b(g)(5) and range from attacks on aircraft to hostage-taking to material support.10Office of the Law Revision Counsel. 18 U.S.C. 2332b – Acts of Terrorism Transcending National Boundaries
Pretrial Detention
Under 18 U.S.C. 3142(e), defendants facing certain terrorism charges are subject to a rebuttable presumption of pretrial detention. If a court finds probable cause to believe the defendant committed an offense under 2332b or any offense listed in 2332b(g)(5)(B) carrying a maximum sentence of at least 10 years, the law presumes no conditions can protect the public. Release is rare.11Office of the Law Revision Counsel. 18 U.S.C. 3142 – Release or Detention of a Defendant Pending Trial
Extended Statute of Limitations
For noncapital terrorism offenses listed in 2332b(g)(5)(B), prosecutors have eight years to bring charges rather than the standard five. If the offense resulted in or created a foreseeable risk of death or serious bodily injury, there is no limitations period at all.12Office of the Law Revision Counsel. 18 U.S.C. 3286 – Extension of Statute of Limitation for Certain Terrorism Offenses
Supervised Release
After a prison sentence for an offense listed in 2332b(g)(5)(B), a defendant can be placed on supervised release for “any term of years or life.” Federal courts can impose lifetime supervision, well beyond what applies to most federal crimes.13GovInfo. 18 U.S.C. 3583 – Inclusion of a Term of Supervised Release After Imprisonment
Capital Punishment
The most serious terrorism offenses carry a possible death sentence. Using a weapon of mass destruction that results in death is capital under 18 U.S.C. 2332a.14Office of the Law Revision Counsel. 18 U.S.C. 2332a – Use of Weapons of Mass Destruction Bombing federal property and causing a death is also capital under 18 U.S.C. 844(f).15Office of the Law Revision Counsel. 18 U.S.C. 844 – Penalties In 2022, the Supreme Court reinstated Dzhokhar Tsarnaev’s death sentence in the Boston Marathon bombing case after a lower court had vacated it. Life sentences without parole remain common in terrorism conspiracy cases where the sentencing enhancement applies.