• Lena Raxter

Utilizing Domestic Court Systems to Address the Shortcomings of International Criminal Law

EDITOR'S NOTE: This article was originally published in print under the title, "Prosecution of Terrorism: Utilizing Domestic Court Systems to Address the Shortcomings of International Criminal Law" in the The Criminal Law Practitioner Volume XII, Issue I.


Without first agreeing to a universal definition of terrorism, it is difficult for the international community to develop a consistent system through which States may prosecute terrorism. However, from 1936 to 1981, the international community proposed, and rejected, at least 109 definitions of terrorism. Moreover, no proposed definition complies with the principle of legality and avoids inadvertently including national liberation movements. Consequently, because of this failure to create a universal definition of terrorism, the international community cannot consistently and extensively prosecute acts of terrorism.

This article first argues that, without a universal definition of terrorism, neither prosecution of terrorism within the International Criminal Court nor prosecution within domestic courts using universal jurisdiction are tenable solutions for consistent, widespread prosecution. The article then argues that, to guarantee prompt and consistent prosecution, States should prosecute the underlying acts of terrorism under existing, well-known, and commonly accepted criminal law—i.e., murder, kidnapping, hijacking, and so forth. States should then consider the intent of the perpetrator to commit an act of terrorism as an aggravating factor during sentencing, which would increase the punishment for the defendant. Through this system, the international community would avoid violating the principle of legality and inadvertently including national liberation movements in a definition of terrorism. As a result, scholars could retire the cliché phrase “one man’s terrorist is another man’s freedom fighter” as States would instead be consistent in prosecuting anyone who has violated criminal law.


According to United States Ambassador Francis X. Taylor, “small cells of terrorists have become true transnationalthreats—thriving around the world without a single state sponsor or home base.”[1] However, the inability of States, or even academics, to agree on a universal definition of terrorism has severely impaired the international community’s efforts to develop international rules addressing terrorism.[2] For some, the solution to this issue is to use an international criminal tribunal, such as the International Criminal Court, to prosecute the crime of terrorism. For others, the solution is to adopt national legislation allowing universal jurisdiction to prosecute individuals suspected of terrorism—regardless of whether there is a nexus between the crime, the perpetrator, and the prosecuting State.

This article argues that, because there is no universally accepted definition for terrorism, many of the proposed solutions—such as prosecution through international criminal tribunals or prosecution via domestic courts based on a domestic definition of terrorism—are ultimately untenable solutions for widespread prosecution of the crime of terrorism. In the interest of prompt prosecution, rather than creating different prosecutorial regimes based on State-specific definitions of terrorism, States should prosecute the acts of terrorism under existing, commonly accepted criminal law—such as murder, kidnapping, hijacking, etc.—and consider the intent of the perpetrator to commit an act of terrorism as an aggravating factor during sentencing.

Lastly, considering that terrorism within the context of armed conflict is governed by the rules of international humanitarian law, this article will focus on analyzing terrorism outside of the context of armed conflict within the meaning of the Geneva Conventions.[3]


A. Definition of Terrorism

The task of creating a universal definition for terrorism is so elusive that it has been described as “resembl[ing] the Quest for the Holy Grail.”[4] Between 1936 and 1981, the international community proposed, and subsequently rejected, at least 109 possible definitions of terrorism.[5] The oft-quoted cliché “one man’s terrorist is another man’s freedom fighter”[6]is, unfortunately, a fairly accurate description for the issues faced by the international community when attempting to adopt a universally accepted definition of terrorism.

1. International legal instruments pre-9/11

One of the earliest attempts to produce a general definition of terrorism occurred in 1937 when the League of Nations created the Convention for the Prevention and Punishment of Terrorism (“1937 Convention”), after a Macedonian nationalist assassinated Alexander I of Yugoslavia.[7] Under this convention, terrorism was defined as: “[a]ll criminal acts directed against a State and intended or calculated to create [a] state of terror in the minds of particular persons or a group of persons or the general public.”[8] However, despite successfully formulating a definition of terrorism,[9] the 1937 Convention never entered into force.[10]

The next significant attempt to define terrorism occurred in 1972 when an ad hoc committee of the United Nations (UN) General Assembly was tasked with creating a Draft Comprehensive Convention that would include a universal definition of terrorism.[11] However, the committee was ultimately unable to complete this task, and instead produced a report that highlights the significant issues involved in drafting a universal definition.[12] The most controversial of these issues was whether “national liberation movements” (“NLMs”)[13] would be included within the universal definition of terrorism.[14] Consequently, instead of producing a definition, the committee opted for creating a framework of conventions addressing specific forms of terrorism on which international consensus could be reached.[15]

With the end of the Cold War and Apartheid in the 1990s, the resulting shift in global politics led to a breakthrough in the quest to create a universal definition of terrorism: the 1994 Declaration on Measures to Eliminate International Terrorism (“1994 Declaration”).[16] Though non-binding, the resolution strongly condemns terrorism and reiterates that “criminal acts intended or calculated to provoke a state of terror in the general public, a group of persons or particular persons for political purposes are in any circumstance unjustifiable, whatever the considerations of a political, philosophical, ideological, racial, ethnic, religious or other nature that may be invoked to justify them.”[17] Scholars have subsequently interpreted this language as defining terrorism in a manner that “divorc[es] the condemnation of terrorism from the value judgment about the reasons that may underpin it.”[18]

Considering this breakthrough, the UN General Assembly once again established an ad hoc committee tasked with creating a Draft Comprehensive Convention.[19] Nevertheless, the committee again failed to fulfill this mandate; however, it indirectly led to the creation of the 1999 Convention for the Suppression of Financing of Terrorism (“1999 Financing Convention”).[20]

2. International legal instruments post-9/11

The events of 9/11 spurred an unparalleled consensus in the condemnation of international terrorism, which resulted in the adoption of a series of significant regulatory documents. For instance, the UN Security Council passed resolution 1373 (2001), which calls upon Member States to cooperate to prevent and suppress the financing, preparation, and commission of “terrorist acts”; however, it provides no definition or clarification regarding what would be classified as a “terrorist act.”[21] The Security Council also passed resolution 1566 (2004), which recalls that:

[C]riminal 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.[22]

Despite the unparalleled international consensus, the efforts to create a universal definition for the UN Draft Comprehensive Convention were fraught with the same divisions that impeded prior efforts. The Convention includes an informal definition: “unlawful and intentionally causing (a) death or serious bodily injury to any person; (b) serious damage to public and private property, including a State or government facility; or (c) other such damage where it is likely to result in major economic loss” provided that “the purpose of the conduct, by its nature or context, is to intimidate a population or to compel a Government or an international organization to do or abstain from doing any act.”[23] Even so, this definition has been criticized for its “breadth and vagueness of terms,”[24] as well as its potential application to NLMs.[25]

B. Customary Elements of Terrorism

Nevertheless, while there is no State consensus on a universal definition of terrorism, various international legal documents have addressed specific types of terrorism or created general legal tools that can be used to address conduct that would commonly be classified as “acts of terrorism.”[26] Further, in 2011, the Appeal Chamber decision of the Special Tribunal for Lebanon (“STL”)[27] controversially concluded that there is, in fact, a definition of terrorism under customary international law.[28] However, scholars and legal experts widely disagree with this conclusion.[29]

Despite the lack of consensus, elements for the crime of terrorism can be identified through various sources. For example, since 1994, various resolutions of the UN General Assembly have defined terrorism as “criminal acts intended or calculated to provoke a state of terror in the general public, a group of persons or particular persons for political purposes are in any circumstances unjustifiable.”[30] Consequently, the elements that can be identified are: (1) the conduct of the accused; (2) the purpose or motive of the act; (3) who or what is targeted by the conduct; (4) a transnational element to the conduct; and (5) classification of the accused.

1. Conduct

The conduct of the accused, also known as the actus reus or material element of the offense, varies widely.[31] In the above General Assembly definition, this is encompassed within the provision, “criminal acts.” The UN Security Council further elaborated on this element in resolution 1566, which adds within its limits those acts “which constitute offences within the scope of and as defined in the international conventions and protocols relating to terrorism.”[32] In some treaties—such as the 1994 Declaration—any “criminal act” is sufficient to fulfil this element.[33] Further, other treaties—such as the European Council Framework Decision on Combating Terrorism[34]—“inchoate” offenses[35] are considered sufficient to fulfill this element.[36] However, in another subset of treaties—such as the 1999 Financing Convention—this element is very restrictive: only acts that cause death or serious bodily injury are sufficient for the element to be fulfilled.[37]

2. Purpose or motive

Unlike other crimes, terrorism generally involves at least two subjective layers, meaning it is a dolus specialis crime.[38]First, the accused must have the intent to commit the underlying act—i.e., intent to bomb, intent to hijack, or intent to cause death or serious bodily harm.[39] Second, the accused must intend that his or her actions will cause broader effects, such as creating a state of terror in a population or compelling a government or organization to act—or refrain from acting—in a specific manner.[40] In compliance with the general principles of criminal law, personal motive is irrelevant.[41] In the above General Assembly definition, this element is encompassed within the provision, “intended or calculated to provoke a state of terror.” Further, the double intent is embodied in UN Security Council resolution 1566, which defines this element as acts “committed with the intent to cause death or serious bodily injury, or taking of hostages, with the purpose to provoke a state of terror, … intimidate a population or compel a government or an international organization to do or to abstain from doing an act.”[42]

3. Targeted “victims” of the conduct

In the above General Assembly definition, this element is encompassed within the provision, “in the general public, a group of persons, or particular persons for political purposes.”[43] However, depending on which source is referenced, definitions will differ on who, or what, must be the target of the conduct. According to the 1937 Convention, the conduct must target a State.[44] However, according to the 1999 Financing Convention, any conduct targeting civilians or other persons not directly participating in armed conflict is sufficient.[45] An even broader scope of activities is sufficient according to the failed UN Draft Comprehensive Convention, wherein any injury or damage occur to any person or property, whether public or private, is sufficient.[46] One criticism of the definition provided by the Appeals Chamber of the STL is that it did not include this element, and therefore applied a similarly broad definition as was included in the failed UN Draft Comprehensive Convention.[47]

4. Transnational element

As noted by the Appeals Chamber of the STL, the transnational element “will typically be a connection of perpetrators, victims, or means used across two or more countries” but it may also involve “a terrorist attack that is planned and executed in one country” which “threaten[s] peace and security, at least for neighboring countries.”[48] However, the exception to this requirement is non-international conflict—which may be a war crime under international law—and “international terrorism” as defined in regional terrorism instruments—which do not normally require this element be met.[49] The above General Assembly definition does not include a provision that encompasses this element.

5. Classification of the accused

This is the most contentious element.[50] As the Special Rapporteur for Terrorism and Human Rights explained, “the term ‘terrorism’ carried almost always the flavour[sic] of some (subjective) moral judgment: some classes of political violence are justified whereas others are not.”[51] In reviewing the action of the General Assembly and the Commission on Human Rights, as well as various other documents, the Special Rapporteur concluded that “as this issue has progressed, [the discussions] reveal that a certain degree of consensus has been obtained on some of the elements of conduct that comprise terrorism, but not on who can use terrorism.”[52] Specifically, the international instruments differ in their inclusion of (a) State-sponsored terrorism;[53] (b) State conduct as constituting terrorism;[54] and (c) conduct of NLMs as constituting terrorism.[55]

Because of the contentious nature of the above three categories, States and scholars alike have found it almost impossible to agree on which should be included or excluded from the scope of a universal definition of terrorism. Nevertheless, because the above General Assembly definition contains the provision “for political purposes,” it could be argued that this element is addressed by outlawing any political justification for terrorism—no matter who commits it. This element was not, however, included in the customary definition provided by the Appeals Chamber of the STL.[56]

C. State-specific Definitions of Terrorism

Particularly after 9/11, multiple States outlawed “terrorist acts” within their domestic criminal code.[57] Most of the definitions use in these domestic criminal codes include a majority of the identified customary elements of terrorism. For example, under current United States (US) domestic law, “international terrorism” is defined as:

activities that—(A) involve violent acts or acts dangerous to human life that are a violation of the criminal laws of the [US] or of any State, or that would be a criminal violation if committed within the jurisdiction of the [US] or of any State; (B) appear to be intended—(i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and (C) occur primarily outside the territorial jurisdiction of the [US].[58]

In another example, under current domestic law in the United Kingdom (UK), terrorism is defined as:

the use or threat of action where—(a) the action [involves serious violence against a person; involves serious damage to property; endangers a person’s life, other than that of the person committing the action; creates a serious risk to the health or safety of the public or a section of the public; or is designed seriously to interfere with or to seriously disrupt an electronic system], (b) the use or threat is designed to influence the government or an international governmental organization or to intimidate the public or a section of the public, and (c) the use or threat is made for the purpose of advancing a political, religious, racial, or ideological cause.”[59]

The most significant issue with the above definitions, as well as the definitions used by other States, is the potential applicability to peaceful protestors or other NLMs.[60] For example, in China, under the guise of combatting terrorism, the Chinese government has repressed and imprisoned peaceful Xinjiang Uighur separatists.[61] Similar exploitation has occurred in Russia with the Chechnian separatists; in Uzbekistan with the independent Islamic congregations and followers, who the government claims are part of the Islamic Movement of Uzbekistan; and in Malaysia with political dissidents.[62]

Indeed, the issue is so dangerous that the International Commission of Jurists recommended that “States should not use the fight against terrorism as a pretext to adopt measures which unlawfully restrict the rights to freedom of expression, religion, opinion and belief, nor the rights of minorities.”[63] Moreover, any anti-terrorist laws which have the potential to infringe upon “human rights and civil liberties should be considered carefully by legislative bodies,” taking account of the relevant requirements established by international human rights law and the relevant jurisprudence.[64]

D. The Principle of Legality

Another vital consideration for the prosecution of terrorism is the principle of nullum crimen sine lege—“no crime without law”—also known as the principle of legality. This principle is codified in Article 15 of the International Covenant on Civil and Political Rights (ICCPR), which reads “nothing in this article shall prejudice the trial and punishment of any person for any act or omission which, at the time when it was committed, was criminal according to the general principles of law recognized by the community of nations.”[65] The purpose of this general principle is to “prevent the prosecution and punishment of a person for acts which were reasonably, and with knowledge of the laws in force, believed by that person not to be criminal at the time of their commission.”[66] Stated differently, the principle prevents a person from being prosecuted for an act which was not criminal at the time the act was committed, or which was ambiguously criminalized.[67]

In practice, the principle of legality requires that “penal statutes must be strictly construed,” and clarifies that the “paramount duty of the judicial interpreter [is] to read into the language of the legislature, honestly and faithfully, its plain and rational meaning and to promote its object.”[68] Moreover, when a criminal statute contains an ambiguous provision, the benefit of the doubt is given to the subject—and against the legislature, which has failed to properly explain itself.[69]

In the context of prosecution for terrorist activity, the principle of legality complicates the prosecution of individuals due to ambiguity in the definition of terrorism.[70] Consequently, while many States and international documents outline the elements of terrorism, it is possible that many of these definitions may not comply with the principle of legality, effectively rendering them null and void.[71]


A. Prosecution via an International Criminal Tribunal

Within international criminal law, there are two ways to prosecute terrorism outside of domestic courts: (1) create an ad hoc international criminal tribunal with the mandate of prosecuting terrorism; or (2) utilize the existing International Criminal Court (ICC) to prosecute terrorism. However, for several reasons outlined below, neither of these options are feasible for the widespread prosecution of acts of terrorism.

1. Prosecution using a new ad hoc international criminal tribunal

International criminal tribunals are responsible for prosecuting crimes which qualify as a grave breach of international law, meaning the crime is so heinous and repugnant that all States may exercise jurisdiction to punish the perpetrators.[72]However, international criminal tribunals have rarely addressed the crime of terrorism, or inciting terror against a civilian population, outside of the context of armed conflict.[73] Of the many ad hoc tribunals, only one—the STL[74]—had the jurisdiction to try the crime of terrorism, and this was due to the incorporation of the domestic Lebanese crime of terrorism as found in the Lebanese Criminal Code.[75] This is largely because there is no universal definition for terrorism.[76]

In order to create an ad hoc international criminal tribunal, the UN Security Council would need to pass a resolution under its Chapter VII powers.[77] This would require two things: (1) the existence of a threat to international peace and security;[78] (2) the cooperation of all five of the permanent members in the Security Council.[79] With respect to the first element, it is likely that the Security Council will consider terrorism a threat to peace and security.[80] However, in respect to the second element, it is improbable that all five permanent members will either vote “for” or “abstain” on a resolution creating a new ad hoc tribunal because there is no universal definition and existing definitions are highly contentious.[81] As a result, it is unlikely that the permanent five members will agree on either the creation of an ad hoctribunal to prosecute terrorism, or a universal definition that the tribunal would apply when prosecuting accused terrorists. Consequently, this is an infeasible option for prosecuting terrorism.

2. Prosecution within the International Criminal Court

In order to prosecute a case in front of the ICC, a series of different criteria must be met,[82] out of which two are most important when determining whether the Court may prosecute an act of terrorism. First, the Court must be able to exercise jurisdiction over the perpetrator. Second, the crime must qualify as at least one of the four crimes for which the Court has substantive jurisdiction.

In order to exercise jurisdiction over a perpetrator, at least one of the following pre-conditions to jurisdiction must be met: (1) the accused is a national of a State Party to the Rome Statute—i.e., the nationality principle, (2) the crime occurred on the territory of a State Party to the Rome Statute—i.e., the territorial principle; (3) the case is referred to the ICC by the UN Security Council, which allows the Court to investigate a non-State Party without first obtaining their consent; (4) anon-State Party accepts the jurisdiction of the Court via an ad hoc declaration permitting the ICC to exercise jurisdiction over their territory for a certain period of time.[83]

Should the above criteria be fulfilled, the international community faces a second hurdle: the ICC only has substantive jurisdiction over four crimes—crimes against humanity, war crimes, genocide, and crimes of aggression.[84]Consequently, in order to use the ICC to prosecute the crime of terrorism, the Assembly of States Party would need to amend the constitutive document of the Court—the Rome Statute—to include the crime of terrorism,[85] or the Office of the Prosecutor would need to prosecute an act of terrorism as one of the existing crimes for which the Court has jurisdiction. Unfortunately, each of these methods has significant drawbacks which make their widespread application unlikely.[86]

i. Amending the Rome Statute to include the crime of terrorism

During the Rome Conference, in which 160 States met to create the ICC, the drafters considered adding terrorism as a crime for which the ICC would have jurisdiction.[87] Regrettably, “no generally acceptable definition of the crimes of terrorism and drug crimes could be agreed upon for the inclusion, within the jurisdiction of the Court.”[88] Nevertheless, scholars have continued to debate the merits of extending the Court’s mandate to include the prosecution of terrorism.[89]

As noted above, there are identifiable elements to the crime of terrorism within customary international law. However, despite the existence of these elements—and their repeated recognition by scholars—States have continued to disagree on the proper permutation of the elements that would form a universal definition. Consequently, it is improbable that States can draft a non-contentious article providing the criteria for the prosecution of terrorism.[90] More importantly, once the article is drafted, it must then be adopted by the Assembly of States Party, which has already failed to find an agreed upon definition, and then ratified by a sufficient number of States Party. It is therefore unlikely that terrorism will be added to the Rome Statute as a crime for which the Court has jurisdiction.

ii. Prosecuting terrorism as a Crime Against Humanity

Depending on jurisdiction and context, international criminal tribunals have defined a crime against humanity differently.[91] However, under article 7 of the Rome Statute, a crime against humanity is the commission of one of the enumerated acts “when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack.”[92] Further, while a crime against humanity should be in furtherance of a State or organization policy to attack a civilian population, it does not have to be attributable to a State.[93] Consequently, the act of terrorism’s degree of scale is the determinative factor for whether or not the act will qualify as a crime against humanity.[94] This would be established through evidence that the act, or series of acts, are committed as part of an identifiable plan or policy.[95] For instance, if the act of terrorism is sporadic or random—such as the 2019 London Bridge stabbing[96]—it is unlikely to meet the required element of “sufficiently widespread or systematic.”[97] Nevertheless, a single act of immense magnitude—such as the 9/11 attacks—may qualify as a crime against humanity due to its mass scale.[98]

Considering the above, it is possible that an act of terrorism may fulfill the substantive criteria necessary to be prosecuted in the ICC as a crime against humanity.[99] However, such prosecution would be highly situation and fact dependent. As a result, while it may be a supplemental means for prosecution in special circumstances, this is not a practical method for the international community to rely on for the widespread prosecution of terrorism.

iii. Prosecuting terrorism as a War Crime

Both the International Criminal Tribunal for Yugoslavia and the STL have found that acts of terrorism may constitute war crimes.[100] However, in order for an act to constitute a war crime within the ICC, an international or non-international armed conflict must exist.[101] As a result, the rules of international humanitarian law apply.[102] Analyzing the applicability of prosecution under this offense is therefore outside of the scope of this article.[103]

iv. Prosecuting terrorism as a crime of Genocide

Under the Convention on the Prevention and Punishment of Genocide, the crime of genocide requires the commission of one of the enumerated acts “committed with the intent to destroy, in whole or in part, a national, ethnical, racial or religious group.”[104] The enumerated acts are limited to (a) the killing of members of the group; (b) causing serious bodily or mental harm to members of the group; (c) deliberately inflicted on the group conditions of life calculated to bring about its physical destruction, in whole or in part; (d) imposing measures intended to prevent births within the group; or (e) forcibly transferring children of the group to another group.[105] This formulation was adopted in article 6 of the Rome Statute.[106]

Consequently, while it is theoretically possible that an act of terrorism could be prosecuted as an act of genocide, two fundamental conditions must first be satisfied. First, the terrorist act must qualify under one of the five categories of enumerated acts. Second, the prosecution would have to prove that the perpetrator committed the enumerated act with the intent to destroy a national, ethnical, racial, or religious group.[107] As a result, similar to prosecuting an act of terrorism as a crime against humanity, prosecution as an act of genocide would be highly situation and fact dependent. It should therefore be considered a supplemental method to be used in special circumstances, rather than as a common method to prosecute terrorism.[108]

v. Prosecuting terrorism as a Crime of Aggression

The crime of aggression was added to the jurisdiction of the ICC during the 2010 Review Conference, and it did not come into force until July 17, 2018.[109] However, scholars doubt whether the crime of aggression will be prosecuted soon because of how narrow it is defined.[110] Article 8bis defines the crime of aggression as

the planning, preparation, initiation or execution, by a person in a position effectively to exercise control over or to direct the political or military action of a State, of an act of aggression which, by its character, gravity and scale, constitutes a manifest violation of the Charter of the United Nations.”[111]

Consequently, to prosecute an individual for the crime of aggression: (1) the perpetrator must be a member of the senior leadership; (2) the crime must be a manifest violation of the UN Charter, as determined by its character, gravity, and scale; (3) the crime must be committed by one State Party against another State Party, unless the crime was referred to the ICC by a UN Security Council resolution; and (4) the States involved must both have ratified the amendment adding article 8bis.[112] The only acts of terrorism which would fall under the jurisdiction of the crime of aggression would therefore be those acts committed by a State against another State, provided that both have ratified the amendment.[113] That would exclude all acts of terrorism by non-State actors, which constitute a majority of terrorist acts.[114] Further, the only individuals who could be prosecuted would be those in senior leadership. As a result, this is not a practical method through which the international community could pursue the widespread prosecution of terrorism.

B. Prosecution within Domestic Courts

While international criminal law allows for the prosecution of terrorism through international criminal tribunals, States may also prosecute terrorism within domestic courts.[115] States may do so in several circumstances, the most common of which are: (1) when the State is party to a treaty outlawing the acts committed by the accused terrorists; (2) when the State invokes one of the five justifications for jurisdiction—territorial, passive personality, active personality, the protective principle, or the universal principle; or (3) when the State prosecutes the perpetrator based on the violation of common domestic criminal law, such as murder, assault, etc.[116] While the first two circumstances are viable options for prosecution, both involve serious issues in their implementation—most importantly, violations of the principle of legality, and inconsistent implementation because there is no universal definition for “terrorism.” The third circumstance, on the other hand, circumvents these serious issues. Through the third circumstance, States may implement domestic legislation in which the domestic court treats the second layer of intent for terrorism—“intent to cause broader effects”—as an aggravating factor during sentencing.

1. Prosecution under existing treaties

A subset of treaties allows for the exercise of jurisdiction based on customary grounds[117]—meaning, if the crime falls within the prescribed conditions, the State is capable of exercising jurisdiction.[118] Under another subset of treaties, the State is required to “prosecute or extradite” (aut dedere aut judicare)—meaning, whether or not the State has jurisdiction under customary grounds, the State must either prosecute the accused or extradite the accused to a State that will prosecute.[119]

However, two significant issues make widespread reliance on prosecution using the law established in existing treaties untenable. First, if a State is party to a treaty that prohibits the conduct committed, the State is required to implement laws which can be used to prosecute the offender.[120] However, if the State is not party to the treaty, the State is not bound to do so.[121] This results in inconsistent application of treaty provisions within the international community as a whole. Second, because there is no universal definition of terrorism, most international legal instruments either address a component of terrorism[122] or include a variation on the definition of terrorism.[123] This results in inconsistent application of the rules regarding prosecution for acts of terrorism, dependent not on the acts but rather on the treaty to which the State is party, and further impedes consistent application of criminal law within the international community. Consequently, this is not the best method through which the international community should pursue the widespread prosecution of terrorism.

2. Exercising jurisdiction over an act of terrorism

For a State to bring a criminal case against an individual, the State must have jurisdiction over the crime.[124] There are three categories of jurisdiction: (1) jurisdiction to prescribe, meaning the ability of the State “to make its laws applicable to persons, conduct, relations, or interests;” (2) jurisdiction to adjudicate, meaning the ability of the State “to subject persons or things to the process of its courts or administrative tribunals;” and (3) jurisdiction to enforce, meaning the ability of the State “to induce or compel compliance or to punish noncompliance with its laws or regulations.”[125] Under customary international law, a State must have the jurisdiction to prescribe in order to bring a case against an individual.[126] Such jurisdiction would exist provided one of the following customary grounds for jurisdiction applies: (1) territorial principle; (2) the active personality principle; (3) the passive personality principle; (4) the protective principle; or (5) the universality principle.[127]

i. Territorial Principle

Under the territorial principle, a State may exercise jurisdiction to prosecute a crime if the act was wholly or partially committed on the territory of the State; had a substantial effect on the State’s territory; or was intended to have a substantial effect on the State.[128] This is the most common basis for jurisdiction.[129] For example, the territorial principle is one of the four methods through which the ICC may exercise jurisdiction.[130] Consequently, States will often use this basis for jurisdiction to prosecute those accused of terrorism within their domestic courts.

ii. Active Personality Principle

The active personality principle, also known as the “nationality principle,” permits jurisdiction when the perpetrator is a national of the State prescribing or prosecuting undesirable conduct.[131] It is one of two justifications that are ratione personae, meaning the jurisdiction is exercised “by reason of the personality involved.”[132] As with the territorial principle, this form of jurisdiction is commonly accepted; for example, the active personality principle is the second of the four methods through which the ICC may exercise jurisdiction.[133]

This principle relies on the concept of nationality—i.e., by virtue of an individual’s nationality, he or she is entitled to a series of rights granted by the State,[134] as well as being subject to a series of obligations[135].[136] However, because international law does not prescribe the conditions through which nationality may be granted, it is up to the State to determine how to grant nationality.[137] There are three generally accepted situations where a State will grant nationality: (a) the individual’s parents are nationals of the State (jus sanguinis); (b) the individual was born within the territory of the State (jus soli); or (c) the individual completed a naturalization process to become a national of the State.[138]

While many States will exercise jurisdiction over their nationals for crimes committed on foreign territory, many others restrict such jurisdiction to only the most serious crimes.[139] Nevertheless, due to the heinous nature of acts of terrorism, a domestic court would likely be able to prosecute a national of their State perpetrates such acts. Consequently, this basis of jurisdiction may be used to prosecute acts of terrorism within domestic courts.

iii. Passive Personality Principle

Under the passive personality principle, a State may prosecute the perpetrator of a crime committed on foreign territory when the crime has, or will, affect nationals of the State.[140] It is the second of the five justifications that is ratione personae.[141] However, this is a controversial basis for jurisdiction.[142]

The passive personality principle was first used by Mexico in the Cutting Case (1887), where a Mexican national sued a US citizen for allegedly libeling the Mexican national in the US.[143] Later, it was used in the S.S. Lotus (1927) case, when Turkey prosecuted a French national for the collision of a French and Turkish vessel on the high seas which resulted in the death of Turkish nationals.[144] In both cases, the States of the accused strongly protested the exercise of jurisdiction over their nationals; however, neither case resolved the issue of whether passive personality jurisdiction is valid.[145] There is continued controversy over the principle, with the Restatement (Third) of Foreign Relations Law claiming that the passive personality principle has not been generally accepted for ordinary torts or crimes.[146]

All this being said, the passive personality principle “is increasingly accepted as applied to terrorist . . . attacks on a State’s nationals by reason of their nationality, or to assassinations of a State’s diplomatic representatives or other officials.”[147] Under the International Convention against the Taking of Hostages, jurisdiction may be established based on the nationality of the hostage “if [the State of nationality] considered it appropriate.”[148] A similar approach is taken in the Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons[149] and the Convention against Torture.[150]

Further, following the 1986 Achille Lauro terrorist attack, the US adopted the Omnibus Diplomatic Security and Anti-Terrorism Act, which allowed for jurisdiction over homicide or physical violence against a US national, regardless of whether the violence occurred in US territory.[151] More recently, in United States v. Yunis (No. 2),[152] the US federal court prosecuted a Lebanese national suspected of hijacking a Jordanian airline outside of the territorial US, based on the fact that the airplane had several American nationals onboard.

As ICJ Judges Higgins, Koojimans, and Buergenthal noted in their joint separate opinion in the Congo v. Belgium (Arrest Warrant) case, while the passive personality principle was previously widely unaccepted, “today [it] meets with relatively little opposition.”[153] As a consequence, States are likely to assert this means of jurisdiction in order to try perpetrators of terrorism within their domestic courts.

iv. Protective Principle

This is another controversial base for jurisdiction.[154] Under the protective principle, a State may assert jurisdiction over the conduct of nationals and non-nationals, committed outside of the State’s territory, due to the fact that the act was directed against critical State interests or functions and therefore affected—or was intended to affect—the prosecuting State’s security or vital interests.[155] Such crimes may include currency counterfeiting, drug trafficking, and human trafficking.[156] The justification for this form of jurisdiction is the protection of a State’s interests, considering that the crime committed may not be an offense under the laws of the perpetrator’s nationality or of the territory in which the offense was committed.[157] Treaties which provide multiple grounds for jurisdiction over particular offenses will often include the protective principle.[158]

Considering the globalized nature and impact of terrorist attacks on the national security of States—and the international community as a whole—acts of terrorism will often fall within the category of applicable crimes.[159] Consequently, this basis of jurisdiction may be exercised to try the perpetrator of an act of terrorism who is not a national of a State and the act was not committed on the territory of the State, but the act did—or would have—affected the interests and security of the State.[160]

v. Universal Jurisdiction

Under universal jurisdiction, also known as “the universal principle,” when an accused commits acts which are particularly offensive and/or threaten the international community as a whole, any State may define and prescribe punishment for the conduct, whether or not there is a nexus between the perpetrator, the crime, or the prosecuting State.[161] Historically, universal jurisdiction was limited under customary international law to situations where crimes “(1) are universally condemned by the community of nations; and (2) occur either outside of a State, or where there is no State capable of punishing, or competent to punish, the crime (as in a time of war).”[162] However, the Restatement (Third) of Foreign Relations Law included “universal jurisdiction,” defining it as the ability to “define and prescribe punishment for certain offenses recognized by the community of nations as of universal concern.”[163] The Restatement further provides examples of these offenses: piracy, slave trade, genocide, war crimes, attacks on or hijacking of aircraft, and possibly certain acts of terrorism when the State otherwise lacks the jurisdiction to prescribe.[164] Other crimes that may also fall into this category include torture and crimes against humanity.[165] Nevertheless, despite the inclusion of terrorism within the Restatement, the expansion of the classic understanding of universal jurisdiction to include terrorism is heavily debated.[166]

Courts in the UK, Spain, Belgium, Switzerland, France, and Germany have invoked universal jurisdiction as a means through which to try cases.[167] However, the ability to prosecute via universal jurisdiction is not automatic; States must enact national laws allowing for the regulation of conduct abroad by non-nationals against non-nationals.[168] Three conditions must be met for universal jurisdiction to apply: (1) there is specific grounds for universal jurisdiction; (2) there is a clear and precise definition of the crime and of its constitutive elements; and (3) there is a national mechanism through which the judiciary of the State may exercise jurisdiction over the crime.[169] Especially after the adoption of the Rome Statute, an increasing number of States have implemented universal jurisdiction legislation.[170] Further, in 2001, a group of international scholars and jurists attempted to clarify the principles of universal jurisdiction by developing the Princeton Principles on Universal Jurisdiction.[171] However, the Princeton Principles’ practical effect is unclear.[172]

Crimes may also be subject to “universal jurisdiction” based on international treaties or agreements.[173] For instance, some treaties create a “prosecute or extradite” (aut dedere aut judicare) regime—essentially creating universal jurisdiction through provisions of the treaty.[174] However, under a “prosecute or extradite” regime, a State must have physical possession of the accused.[175] Consequently, such a regime is not the same as “pure” universal jurisdiction, which does not require that the prosecuting State have possession of—or any other nexus to—the accused.[176]

Universal jurisdiction has been vital in prosecuting crimes that would otherwise have gone unpunished.[177] However, universal jurisdiction is subject to several limitations, including the potential for abuse.[178] For example, the lack of a universal definition for terrorism means States with opposing interests to NLMs could attempt to prosecute foreign individuals for crimes committed during civil unrest in foreign States.[179] Further, after adopting legislation authorizing expansive universal jurisdiction, public pressure has caused some States to amend the legislation to limit jurisdiction.[180] Lastly, considering the backlash to “pure” universal jurisdiction statutes, it is unlikely that such jurisdiction could be used to prosecute a perpetrator unless some form of nexus exists between the perpetrator, the crime, and the prosecuting State.[181]

3. The issue of state-specific definitions

As seen above, there are a myriad of different methods through which a domestic court may exercise jurisdiction over a perpetrator. Nevertheless, as Judge Cassese says, “however imperfect and incomplete, a common working definition is necessary so all concerned may agree on the target of their repressive action: how can states work together for the arrest, detention or extradition of alleged terrorists, if they do not move from the same notion?”