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  • Boaz Ganor

MIA: An International Definition for Terrorism

The lack of a universal definition for the term “terrorism” enables some states to say they stand against it, while in practice they support it. Global adoption of a single definition would deflate the cliché that "one man's terrorist is another man's freedom fighter" and advance the struggle against terrorism in its most insidious—and hypocritical—forms

An IDF counter-terrorism unit in training, 2016

An IDF counter-terrorism unit in training, 2016 | Photo: Israel Defense Forces/Eden Briand, IDF Spokesperson unit (CC BY-NC 2.0)

On June 30, the National Council of Resistance of Iran (NCRI) held a conference in Villepinte, France. Headed by Maryam Rajavi, the NCRI is an umbrella organization that unites Iranian exiles and opposition groups aspiring to overthrow the Iranian regime. The NCRI is also the de facto political arm of the People's Mujahedin of Iran (Mujahedin Khalq), a group of exiles who support a violent overthrow of the current Iranian government. The conference was attended by ministers from several Middle East countries, Europe, and the United States, including the former mayor of New York and present attorney to the U.S. president, Rudy Giuliani.

Just days before the conference commenced, Belgian security officials executed five raids around the country to foil a terrorist plot targeting conference attendees. The resulting arrests included two Belgian nationals, a husband and wife of Iranian descent in whose car were found an explosive, TATP, and a trigger device. Three other suspects were arrested in France and one in the city of Aschaffenburg, Germany. This suspect arrested in Germany was Assadollah Assadi, 47, an Iranian diplomat stationed at the embassy in Vienna. It was allegedly his task to oversee the unit slated to carry out the plot. He was arrested while making his way to Brussels or Paris to complete preparations for the attack. In parallel to the arrests, the Netherlands expelled two Iranian diplomats suspected of espionage.

According to sources, the attack was planned by members of the Quds Force, a unit of the Iranian Revolutionary Guard Corps, as part of wider effort to employ sleeper cells around Europe to assassinate Iranian exiles and leaders from Sunni Arab countries. According to one source, the blog IntelliTimes, Assadollah led the Iranian intelligence base in Vienna, where he was posted in 2014. Belgium, according to the report, had been chosen as the base country for the Iranian terrorism unit’s logistical branch. Operators settled in Brussels, Antwerp, Mons, and in Leuze-en-Hainaut disguised as new immigrants.

Following the arrests, Israeli Prime Minister Benjamin Netanyahu stated that the European continent had a confusing—and possibly confused—stance vis-à-vis Iran. “That week, and it's an amazing thing, these countries officially invited [Iranian President Hasan] Rouhani,” Netanyahu said. “But at the same time, Rouhani’s government sent its terrorism unit into action in France. The commander of the operation was an Iranian diplomat stationed in Vienna. Fortunately, the plot was exposed. When the suspects were arrested, they had explosives and more in their possession."


Ignoring the need to agree on a international definition of terrorism perpetuates international hypocrisy, and allows players to continue to simultaneously oppose and support terrorism


Netanyahu also intimated that the successful arrests were at least partly thanks to Israel’s intervention. “[W]e act strongly against those who threaten to destroy Israel […]. We do it in the international arena, tearing down one wall after another. Sometimes we have to tear down walls of hypocrisy,” he stated. For his part, the Belgian prime minister, Charles Michel, tweeted that the foiled plot was another victory for international cooperation.

Iran responded to the arrests quickly and forcefully. The government in Tehran summoned the ambassadors of the Netherlands, France, Germany, and Belgium to chide them for the way their countries had handled the incident. Iranian spokespersons publicly stated that instead of expelling Iranian diplomats, the Dutch government should explain why it sheltered members of a terrorist organization. The Iranian Foreign Minister tweeted, Mohammed Javad Zarif, tweeted: “How convenient, just as we embark on a presidential visit to Europe, an alleged Iranian operation and its ‘plotters’ arrested. Iran unequivocally condemns all violence and terror anywhere and is ready to work with all concerned to uncover what is a sinister false flag ploy.”

Javad Zarif twitter post | Photo: twitter

Iran’s response was not unprecedented. Only one year earlier, in 2017, Iran used similar rhetoric to slam that year’s NCRI meeting. That gathering, which included Giuliani, the new American National Security Advisor John Bolton, Senator Joseph Lieberman, and the Saudi prince Turki bin-Faisal, drew wrath and criticism on Iranian social media, where people claimed it constituted Saudi and American aid for terrorism. Thousands of Iranian web commentators compared the Mujahedin Khalq to ISIS and claimed that there was no difference between supporting the Iranian opposition organization and the Islamist terrorism movement. Some even accused the U.S. and other Western powers of hypocrisy. The official response was no less muted. Ali Akbar Velayati, advisor to the Iranian president, remarked after the conference that hosting terrorists hardly contributes to regional and international peace

Politics of Opposites

This back-and-forth blame game between Iran, Israel, and Europe begs the question: Who is the terrorist here? Did Iran and its cohorts attempt to perpetrate a terror attack on European soil? Or was the plan instead a counter-terrorism ploy in its own right, a targeted assassination attempt against members of a terrorist organization that seeks to destroy the Islamic Republic? Is Iran the one that perpetrates and supports terrorism, or is it perhaps the United States and its allies that sponsor such acts?

The reason why this is a difficult question to answer is because there is no clear international definition of terrorism. It is also why international efforts to eradicate terrorism cannot seem to transcend narrow interests and ad hoc cooperation. That being the case, the question remains: Is it possible, in the thicket of international politics, to agree on an underlying definition? And is doing so worth the investment in diplomatic resources and efforts?

One thing is clear: continuing to ignore the intensifying need to agree on a single international definition of terrorism perpetuates international hypocrisy. Without an agreed-upon international definition, multinational alliances and cooperation efforts against terrorism may arise that do serve the particular and immediate needs of whatever nations are involved, but they cannot effectively fight the phenomenon on a global level. This is all the truer as incitement and recruitment increasingly move online, where the boundaries and rules are fuzzy—in turn creating new complications.

In the absence of a universally accepted definition for terrorism or international accord regarding the objective conditions qualifying a group as a terrorist organization, there is almost no coherence to the way different countries classify and treat such organizations. Inevitably, without clear, objective guidelines, the issue becomes political, and countries act according to their individual interests and worldview.


Without clear benchmarks, countries wield their terrorist organization watchlists as a political weapon, designed to further underlying policies


Thus, Iran can view the Mujahedin Khalq as a terrorist organization while concurrently supporting Hezbollah and Hamas. The U.S., on the other hand, classifies Hezbollah and Hamas as terrorist organizations, while in 2012 it removed the Mujahedin Khalq from its list of terrorist organizations. Meanwhile, the U.S. is cooperating with and backing the Kurdish People's Protection Units in Syria, which is defined as a terrorist organization by Turkey, which is fighting it with Russia's help. Moscow, for its part, is fighting Chechen terrorism and defines the Congress of the Peoples of Ichkeria and Dagesta as a terrorist organization—but the Congress of the Peoples does not appear on the U.S. State Department's list of terrorist organizations. And since Russia does not define Hezbollah as a terrorist organization, it has no qualms about allying with the organization to fight those rebelling against the Assad regime in Syria. Russia is even sending arms to Iran and Syria for transfer to Hezbollah.

And that’s not the end of it—or even close. Qatar is helping Hamas, which again the U.S., Israel, and Europe deem a terrorist organization but which the Qatari foreign minister has called a “legitimate resistance movement.” At the same time, Qatar is dealing with sanctions from several Gulf states, which accuse it of sponsoring terrorism. The East Turkistan Islamic Movement, which reflects the nationalist yearnings of the Muslim Uighurs in western China, is defined by the Chinese government as a terrorist organization—but not by the government of the United States. The Japanese cult Aum Shinrikyo, which was responsible for using chemical weapons in terrorist attacks in Japan, is outlawed in Russia and has been defined as a terrorist organization in the U.S. and Canada, but not in Australia. The list goes on.

Without clear benchmarks for these terms, countries wield their terrorist organization watchlists as a political weapon, designed to further underlying policies. While this might be an effective tactic in the diplomatic realm, it is a disaster for the real task at hand—fighting terrorism

The Tired Cliché at the Heart of the Problem

Why is there no international agreement on the definition of terrorism? Is there a genuine difficulty in achieving accord—or is it simply convenient for politicians and powerbrokers to duck the real issues in favor of slippery rhetoric?

The current definitional fuzziness enables political leaders to convene international conferences and demonstrate feigned solidarity for photo ops. At the same time, by defining terrorism according to their whims, they can wield the label against hostile organizations while removing from their national blacklists organizations that they deem “in their camp.”

Those who oppose attempts to develop a universal definition of terrorism cleave to the worn-out cliché that "one man's terrorist is another man's freedom fighter." In theory, the old saying is true enough—but in practice, it is misleading and dangerous. Those living in liberal democracies often accept this erroneous precept, which assumes that terrorism and national liberation are two ends to a spectrum of legitimate violence. Struggle for "national liberation" is ostensibly the good, just end of the continuum, while terrorism is the bad, despised other end. By that logic, an organization cannot simultaneously be a terrorist organization and a national liberation movement.

Senator Henry Jackson illustrated this perspective well. As he said, “[t]he idea that one person's ‘terrorist’ is another's ‘freedom fighter’ cannot be sanctioned. Freedom fighters or revolutionaries don't blow up buses containing non-combatants; terrorist murderers do. Freedom fighters don't send out to capture and slaughter school children; terrorist murderers do." According to Jackson, freedom fighters can be distinguished from terrorists based on the tactics they employ.[1]

Dr. Benzion Netanyahu, late father of Prime Minister Benjamin Netanyahu, similarly believed that true freedom fighters do not commit acts of terrorism. In his view, "in contrast to the terrorist, no freedom fighter has ever deliberately attacked innocents. He has never deliberately killed small children, or passersby in the street, or foreign visitors, or other civilians who happen to reside in the area of conflict.”[2]


Countries should sidestep artificial distinctions between “bad,” “good,” and “tolerable” terrorism to prohibit specific tactics


In truth, this distinction is meaningless. It is of course specious to claim that no “freedom fighter” commits acts of terrorism, murder, or killing. Many freedom fighters in modern history have committed crimes, including purposely targeting civilians. This artificial distinction thus plays into the hands of terrorists who argue that since their aim is to expel what they see as a foreign occupier, they cannot be considered terrorists. The cliché that "one man's terrorist is another man's freedom fighter" is wrong and misleads because at its heart, terrorism is a tactic, not a goal. Organizations can easily aspire to national liberation and make use of terrorist attacks to achieve it.

In other words, the current definitional morass leads bystanders to conflate an organization’s goals with its behavior—and that, in turn, muddies the operational response. If the world’s leaders truly wish to curb terrorism, it is imperative that they define it and thus distinguish it from other types of political violence. In parallel, world leaders must determine that a struggle for freedom, or any other political aim—justifiable as it may be in theory—cannot justify the use of terrorism.

More specifically, world leaders must take a stand against the definition of terrorism published by the Muslim World League in Durban, South Africa in 2001. That definition stated, among other things, that:

Terrorism is an outrageous attack carried out either by individuals, groups or states against the human being (his religion, life, intellect, property and honor). It includes all forms of intimidation, harm, threatening, killing without a just cause.[3]

On its face, this definition seems quite broad—it encompasses a great many serious, harmful actions, and deeds—but importantly, it does not prohibit use of these “outrageous” actions as long as they are aimed at achieving an ostensibly “just cause.” Since it is realistically impossible to arrive at international consensus regarding what a justified cause is, any such definition is doomed to fail.

Indeed, this sort of definition is a direct sequel to the misleading argument that terrorism is a subjective thing that depends on the aims of the perpetrators and the legitimacy of those aims. Like the cliché, the Muslim League's definition of terrorism confuses means and ends—and thus stymies any attempt to reach international consensus.

Countries should sidestep artificial distinctions between “bad,” “good,” and “tolerable” terrorism to prohibit specific tactics. The nations of the world have always been at odds over what constitutes a justified aim, or a legitimate or sacred one, because they differ regarding their points of view, ideology, culture, religion, and national interests. However, they could come to agree that regardless whether a purpose is legitimate, using terrorism to achieve it is wrong. Such a definition would establish that “terrorism is terrorism,” no matter who originates it—Muslim, Christian, Jew, or anyone else.

A key step toward such an international consensus did occur in 2004, when the UN Security Council unanimously accepted Resolution 1566. The resolution recognized how serious a threat international terrorism poses to global peace and security, and called on states to take every measure necessary, in compliance with international law and human rights, to fight it. The resolution condemned terrorism in all its forms, irrespective of motivate or the perpetrator’s identity.

Unfortunately, Resolution 1566 failed to actually define the term. Instead, the it attempted, unsuccessfully, to circumvent definitional disagreements by recalling that criminal acts, including against civilians, committed with the intent to cause death or serious bodily injury, or taking of hostages, with the purpose to provoke a state of terror in the general public or in a group of persons or particular persons, intimidate a population or compel a government or an international organization to do or to abstain from doing any act, which constitute offences within the scope of and as defined in the international conventions and protocols relating to terrorism - are under no circumstances justifiable by considerations of a political, philosophical, ideological, racial, ethnic, religious or other similar nature.

Needed: An International Consensus

Most politicians, lawyers and judges, terrorism experts, academics, and leading thinkers claim that it is impossible to achieve an agreed-upon international definition of terrorism. Nor is it even necessary, they continue, because international cooperation in the fight against terrorism exists despite definitional disagreements.

In contrast, those who argue that an international definition of terrorism is necessary—myself included—believe that international counter-terrorism cooperation efforts are dangerously stunted by the lack of global consensus regarding what constitutes the threat. Such consensus is necessary to effectively block terrorist funding sources, disrupt related money-laundering schemes, and foil recruitment efforts. Further, countries cannot agree to an appropriate standard for extraditing arrested terrorists, or on how best to criminalize acts in support of terrorism, when there is no agreement as to what terrorism is, which organizations promote it, and who the terrorists are.

There’s more. Thanks to the internet, international cooperation is more important than ever. How can individual countries stymie attempts to incite terrorism when radicalization channels exist primarily online, where physical boundaries mean nothing, and where a terrorist activist in one country can encourage people in other countries to carry out attacks there?

Many commentators have admonished the companies that operate the relevant social media networks, such as Facebook, Twitter, Instagram, and others, for ostensibly failing to do their part to curb incitement on their platforms. These reactions are unhelpful. Until there is an international consensus regarding the definition of terrorism, there cannot be one regarding incitement to it. Moreover, putting the onus on the companies creates further avenues for abuse. Today governments can demand that these companies block messages that are simply on behalf of their opposition, such as calls for popular protest and demonstrations, by claiming that they are “terrorist incitement.”

A Fox News story on Facebook's shortcoming in addressing terrorism | Source: Youtube

The crisis is heightened by the technological revolution occurring among security and intelligence bodies, which are increasingly relying on computer systems, big data, artificial intelligence (AI), and machine learning to obtain counter-intelligence and to develop early-warning systems. The importance of an international consensus grows several-fold when intelligence systems avail themselves of big databases, using various algorithms to identify terrorists before or after attacks. Technology companies currently claim that they can determine whether a given individual is a terrorist based on routine behavioral analysis (e.g., based on how s/he talks and moves), through processing biotechnological data, and even based on facial recognition analysis. Again, this points to the underlying problem: How can an AI system determine that a given person is a terrorist if there is no international agreement regarding what terrorism is, and hence who a terrorist is?

In his article "How the Enlightenment Ends," Henry Kissinger warns against arbitrarily using AI for security and intelligence purposes while ignoring the ensuing ethical dilemmas. His article references a chatbot called Tay, which was programmed to conduct friendly conversations using the language patterns of a 19-year-old woman. The chat quickly deteriorated into racist, offensive conversation. Kissinger wonders how Tay could learn to recognize "offensive" language when humans do not universally agree as to what the word means. The same question can be asked about terrorism. As long as there is no universal definition for the term, AI systems cannot be expected to learn how to effectively recognize it.

Terrorism: A Proposed Definition

There is no lack of proposed definitions for terrorism. Every academic and expert, every defense official and politician, would be happy to offer his or her own definition, which by the nature of things reflects his or her worldview and, often, political stance. Indeed, in a 1988 publication, the researchers Alex Schmid and Albert Youngman reviewed more than 100 definitions of terrorism.[4] In contrast to these personal interpretations, a universal definition of terrorism must be clear, objective, and global. Further, it must be a political definition of the term—not necessarily a legal one delineating a crime.

As a political definition, the one I propose below does not necessarily adhere to the relevant existing articles of law, international pacts, or UN Security Council resolutions. Rather, it lays down normative principles from which any country or international organization can derive its own codex of laws and regulations. The proposed definition can also serve as a guide for formulating universal legal definitions regarding terrorism crimes.


The term "terrorism" relates to the modus operandi of the perpetrators, while the term "freedom fighters" relates to the purpose the perpetrators are trying to achieve


Any definitive definition must be objective and clear and correspond with the fundamental principles of international law and universal moral values. The definition needs to treat terrorism as a specific modus operandi, distinguishing it from other expressions of political violence. The definition must also correspond with international conventions and UN Security Council resolutions relating to terrorism, and enable the development of new international conventions and the expansion of international counter-terrorism collaborations.

With that background, the proposed definition of terrorism is:

Terrorism is the deliberate use of violence against civilian targets by a non-state actor to achieve political aims.[5]

Stemming from this definition, one can ascertain the following:

  • Terrorism is a prohibited method of operation. This definition does not distinguish between the different justifications underlying terrorist acts, whether social, nationalist, ideological, revolutionary, religious, or other, as long as they are not purely criminal.

  • The material distinction between terrorists and freedom fighters is that the term "terrorism" relates to the modus operandi of the perpetrators, while the term "freedom fighters" relates to the purpose the perpetrators are trying to achieve. Therefore, the aims of liberation and freedom, however legitimate, cannot justify the use of terrorism—that is, deliberately harming civilian targets. An act that meets the definition of terrorism cannot be justified by virtue of serving national “liberation.”

  • This definition corresponds with the basic international principles of war, which hold that even in a state of war, deliberate use of violence against civilians is unacceptable and is a war crime (even if the enemy is also guilty of war crimes).

  • This definition relates to terrorism as acts carried out by non-state entities and individuals. This is partly because the laws governing war have already banned countries from deliberately harming civilians, and such acts are already defined as war crimes or as crimes against humanity. The proposed definition relies on the same normative principle that underlies the theory of war crimes and crimes against humanity: prohibiting deliberately harming civilians.

  • This definition does not take a stand on the right of non-state organizations to use violence to achieve political ends, but it excepts the deliberate use of violence against civilian targets from other violent acts, such as those deliberately targeting military targets.

  • However, this definition does not permit harming military targets and does not rule out the right of any nation to define organizations that target its military as enemies, and to fight them subject to the law of war. The definition effectively indicates that the danger arising from terrorist acts is beyond the threat posed to any given country and requires international action against such acts’ perpetrators.

  • The proposed definition includes any act of deliberate violence against civilian targets, irrespective of the gravity of the resulting harm (other than verbal violence). An act of terrorism is therefore a deliberate act, not one of negligence, and may be carried out in the physical world or in cyberspace.

  • The definition does not employ terms and descriptions that commonly appear in various definitions, such as:

  • "Innocents" – this adjective is eschewed because, in contrast to the objective, measurable term "civilian," "innocent" is a subjective term that depends on the definer's point of view.

  • "Non-combatants" – in contrast, for example, to that of the U.S. State Department's, the proposed definition does not distinguish between combatant and non-combatant military targets. Constraining the definition while relating to deliberate harm to civilian targets enables a clear threshold to be set that may not be crossed.

  • Terror threats – in contrast to many definitions of terrorism, the proposed definition does not define threats as an act of terrorism. Despite the dangers inherent to threats of terrorism, the definition of terrorism must be limited to the prohibition on carrying out of terrorism, not mere threats.

  • Actions designed to sow fear and anxiety – by nature, most terrorist actions aim to sow fear and anxiety—but in many terror attacks, the immediate purpose to kill, sabotage, ransom, and so on, while the communal anxiety resulting from the attack is only a secondary purpose. This element cannot therefore be included in the definition.

  • Illegal – being political in its essence, the definition does not determine what a lawful or unlawful act is—it is, as said, the right of each country to write its own criminal code.


The proposed definition is concise, accurate, and clear, precluding subjective manipulations and interpretations. It is objective and does not take a stand regarding the use of violence by non-state entities to achieve various political ends. And it distinguishes terrorism from other acts of political violence and enables countries and organizations to work together against it, irrespective of their political positions.

The proposed definition not only enables international efforts to prevent terrorist attacks directly, but also to formulate a coherent stance vis-à-vis designating certain organizations as terrorist groups, curb terrorist incitement, extradite terrorists, effectively block terrorism funding, and strengthen multilateral intelligence sharing. It also corresponds with the basic principles of international law and with relevant international treaties and Security Council resolutions.

Further, the proposed definition of terrorism—if adopted by organizations and countries around the world as a binding normative standard—could change terrorist organizations’ cost-benefit considerations. Namely, it could induce them to abandon terrorist tactics (deliberately harming to civilians) in favor of alternative forms of violence. In fact, the definition empowers certain arguments already advanced within terrorist organizations questioning whether deliberately targeting civilians is legitimate.

Finally, the definition would preclude the ways certain terrorist groups currently manipulate the “one man's terrorist is another man's freedom fighter” rhetoric to conceal their true nature.

Today, most states and most political decisionmakers are happy with the current definitional opacity because it gives them room to maneuver and to deny—at the expense of more effective international counter-terrorism efforts. It thus seems that achieving international agreement regarding the term cannot be based on traditional diplomacy, such as through bilateral or multilateral treaties or UN Security Council resolutions. Instead, we need a new, direct kind of diplomacy, via civilian society and global organizations that represent supra-national interests, led by the internet service providers and social networks. It is these players, after all, that most need a clear, independent definition of the phenomenon to eradicate attempts to use their platforms to recruit, train, and incite terrorists.


[1] Benjamin Netanyahu, War on Terrorism, Yedioth Ahronoth, 2004, p. 18

[2] Ibid, p. 24.

[3] Secretary General Makkah Al-Mukarramah, "Terrorism - The Islamic Point of View”, published by the Muslim World League, distributed by the NGO conference in Durban, South Africa, 2001.

[4] Alex P. Schmid and Albert I. Youngman et al., Political Terrorism (SWIDOC, Amsterdam and Transaction Books, 1988).

[5] Boaz Ganor, The Counter-Terrorism Puzzle: A Guide for Decision Makers (Herzliya: Interdisciplinary Center, 2003).

Boaz Ganor

Prof. Boaz Ganor is the Dean and the Ronald Lauder Chair for Counter-Terrorism at the Lauder School of Government, Diplomacy & Strategy, as well as the Founder and Executive Director of the International Institute for Counter-Terrorism (ICT), at the Interdisciplinary Center, Herzliya.

(Photo: from the ICT website)

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