The car ramming attack that occurred in New York City on Oct. 31 killed eight people and reignited debate over what constitutes domestic and international terrorism. Terrorism has remained at the forefront of American national security concerns ever since the September 11 attacks. And as globalization continues to extend its reach, terrorists have demonstrated a dangerous ability to connect with a wide audience through their use of the Internet, as the line that once separated what constitutes an act of “domestic terrorism” versus “international terrorism” appears increasingly blurry.

“September 11 and the subsequent rise of homegrown terrorism has really muddled the traditional line between international terrorism and domestic terrorism,” says Mike Leiter, Cipher Brief expert and former director of the National Counterterrorism Center.

In fact, individuals based in the U.S. who have used trans-nationalist ideologies to fuel their violence, as in the cases of San Bernardino and Orlando attacks, have been labeled as terrorists, even if they had not traveled outside the U.S. to receive any sort of training or indoctrination.

“The link has become relatively tenuous when you are talking about a transnational ideology, which motivates someone who can be born, raised, and basically everything here in the U.S. and then suddenly carries out an act that is labeled as international terrorism as opposed to domestic terrorism,” Leiter explains.

According to Mitch Silber, Cipher Brief expert and former director of intelligence analysis at the NYPD, the classification of an individual as a terrorist holds true whether or not that person was directed by a terrorist organization to carry out an attack or simply motivated by the group’s ideology to commit an act of violence.

“If someone says that they are inspired by ISIS or al Qaeda, then it’s just as legitimate of a terrorist act as if they received a direct message from al Qaeda or ISIS to carry out an operation,” explains Silber.

The distinction between “domestic” and “international” terrorist has particular ramifications with respect to how the U.S. government can and will respond. The way that the United States reacts to an incident that is considered “domestic terrorism” is markedly different from something deemed “international terrorism,” not only in terms of rhetorical treatment, but also due to the way that the American legal system is structured.

Domestic perpetrators, such as the Oklahoma City bomber Timothy McVeigh, plan and carry out their attacks within the territorial boundaries of the United States, so domestic criminal law is applied to investigate, prosecute and punish the attacker or attackers. But the case becomes much more complex when the act of terror is perpetrated by foreign individuals with a chain of accomplices and logistical support that extends into countries where U.S. law cannot reach, as was the case with the 9/11 hijackers.

In order to catch these terrorists, the U.S. must work with foreign countries to extradite these individuals or can conduct targeted strikes to remove them from the battlefield, as permitted by the 2001 Authorization for Use of Military Force (AUMF). In essence, the legal structure built around international terrorism empowers intelligence agencies and law enforcement to use powerful tools to hunt and capture terrorists, including warrantless wiretaps, the ability to develop a wider range of informants under the material support statute, and many more tactics that would not necessarily be available in a case of “domestic” terrorism.

This difference has led to the creation of “a completely different legal regime separating international terrorism from domestic terrorism,” said former undercover FBI agent and fellow at the Brennan Center, Michael German.

That separation has led domestic terrorism to be treated largely as a criminal issue, while international terrorism has come to be treated as a foreign intelligence issue with “a completely different legal structure that doesn’t exist on the domestic terrorism side of things.”

One way to deal with the terrorism from a domestic, legal perspective, is by arresting people who provide material support to foreign terrorist organizations.

“That’s the most frequently used mechanism for arresting people on terrorism-related charges,” Silber explains. “Law enforcement waits until people cross that line of doing something that meets the definition of providing material support to a foreign terrorist organization, and then that is what they are locked up for.”

But according to German, many domestic terrorists who espouse violence, especially at demonstrations such as the one that occurred in Charlottesville, Virginia in August, are still slipping through the cracks, even though they use tactics employed by international terrorist organizations.

“I have been shocked and disappointed at the reaction of law enforcement regarding the increasing violence at these far right protesters,” German says.

“Law enforcement have, for now, taken their eye off the criminal fringe and begun to treat these like any other protests where they’re looking at who the leaders and speakers are rather than recognizing that this is very different. There is organized criminal activity for the purpose of a committing a crime at these events. Some of these people are actually on probation, going from protest to protest committing violence and filming that violence without law enforcement seemingly aware,” he explains.

Ultimately, while the lines between domestic and international terrorism become increasingly murky, Leiter maintains that distinguishing between what constitutes an act of terrorism and what doesn’t still provide significant value.

“Differentiating between terrorism versus non-terrorism violence is still important because depending on the motivation of any violence act, you might have a very different policy response,” says Leiter. “Something that is motivated by an individual simply being crazy versus a political act, you’re going to try to prevent that in different ways, and it may have different consequences on the population.”

Bennett Seftel (@BennettSeftel) is deputy director of analysis at The Cipher Brief, and Fritz Lodge (@FritzLodge) is a Middle East and international economics analyst.

The article appeared in the Cipher Brief on 24/11/2017