1. Introduction
The serial failures in the attempt to define terrorism compelled Justice Richard Baxter of the International Court of Justice (ICJ) to lament when he stated, “we have cause to regret that a legal concept of terrorism was ever inflicted upon us. The term is imprecise; it is ambiguous; and, above all, it serves no operative legal purpose” (Baxter, 1974). His frustration highlights a fundamental legal dilemma which is the persistent ambiguity of the term terrorism. While widely used, the term lacks a singular, universally adopted legal meaning. Notably, this failure at achieving a universal definition has not deterred governments, security agencies, media outlets, and academics frequently invoke “terrorism” to justify far-reaching policy actions, often without interrogating the political and racial undertones such usage implies (Goldberg, 2015). Even more concerning is that the nebulous nature of this definition has become a basis of clandestine counter-terrorism measures, racial profiling, investigations, surveillance, visa bans, economic sanctions and invasion of regions that fall within the ambit of this elusive concept (Golder & Williams, 2004).
This paper critically examines how terrorism has been constructed, both legally and discursively, over time, especially within the UK. It draws on legal instruments, and social theory to demonstrate how terrorism definitions impact the enforcement of laws, the protection of civil liberties, and the treatment of minorities. It further explores the tensions between national and international responses and concludes with practical recommendations for achieving definitional consensus.
2. Perceptions of Terrorism
As established in the introductory words of this paper, terrorism as a concept has long defied singular definition, both in academic and legal discourse. Scholars including Muradi (2024) and Lea et al. (2024) have argued that terrorism is not an objective phenomenon but is rather shaped by the perceptions and interests of governments and institutions. These perceptions are further rooted in political, historical, and social contexts, resulting in shifting meanings of terrorism over time (Esmailzadeh, 2024). This suggests that terrorism is not an ontological reality, but rather a social construct, a label applied to acts of political violence depending on how they align with prevailing ideologies and structures of power (Onuf, 2009).
The constructivist theory of Onuf (2013) demonstrates how social institutions and political actors jointly produce meaning through speech, including what is referred to as “terrorism”. Based on this framework, Holbrook & Horgan (2019) notes that terrorism is the result of interpretive framing rather than an intrinsic characteristic of an act since definitions rely on ideational elements including perception, identity, and ideology. In order to further geopolitical objectives or quell dissent, nations can use this framework to label specific persons or movements as terrorists while ignoring comparable actions by allies (Snow & Byrd, 2007).
The evolution of terrorism’s meaning can be traced historically. During the 1970s and 1980s, left-wing political insurgencies like the Irish Republican Army (IRA) in the UK and the Red Army Faction in Germany were frequently linked to terrorism. As noted by Wilkinson (2019), the IRA’s bombing operations had a direct influence on the UK’s legislative measures, especially the Prevention of Terrorism (Temporary Provisions) Act 1974. This legislation established the basis for extensive counterterrorism powers that still exist today and allowed authorities to hold individuals for prolonged periods of time (Blackbourn, 2011; Bonner, 2019). Notably as well, the 1993 World Trade Center explosion and the 1998 US embassy assaults in Kenya and Tanzania are two examples of the trend toward religiously motivated terrorism that occurred in the 1990s (Musembi, 2018). However, the September 11, 2001 attack, more popularly known as the 9/11 attack was the most significant shift in the global perception of terrorism (Onireti, 2024). The United States and its allies, including the United Kingdom, responded by implementing robust counterterrorism policies that increased racial and religious profiling, especially against Muslims, and expanded surveillance authorities (Choudhury & Fenwick, 2011).
In the UK particularly, post-9/11 securitization manifested through the Prevent Strategy, which sought to pre-empt radicalization. While framed as protective, critics such as Martin (2017) and Mott (2018) argue it disproportionately targets Muslim communities. According to the UK Home Office (2021), 70% of referrals to Prevent in 2020 were related to Islamist extremism, despite rising far-right activity. A 2021 report by Hope Not Hate further revealed that British Muslims were five times more likely than other citizens to be referred to counter-terrorism programs. This selective application of terrorism definitions exemplifies the racialized and politicized nature of securitization (Awan, 2012).
Building upon the securitization theory of the Copenhagen School, scholars like Priya Dixit and Jacob Stump contend that terrorism should be seen as a practice, a method by which particular groups, ideologies, or behaviors are framed as existential threats rather than just a category of violent acts (Dixit & Stump, 2015). This method places a strong emphasis on the institutional interests and political processes that underpin the labelling of actions and events as terrorism. For instance, both the 2017 London Bridge assault and the 2017 Finsbury Park Mosque attack featured acts of mass violence, but the later was quickly classified as terrorism while the former, which was carried out by the far-right, was not at first. This disparity illustrates how race and religion affect how anti-terrorism laws are actually applied.
These disparities gave rise to Critical Terrorism Studies (CTS). CTS, which has its roots in Critical Security Studies, questions the epistemic basis of conventional terrorism research (Oando et al., 2023). It argues that terrorism is politically, socially, and historically contingent and critiques the hegemonies that determine what violence is deemed legitimate versus illegitimate (Jackson, 2007). Scholars within CTS including Al-Kassimi & Simons (2019) aim to reveal the power dynamics behind terrorism labelling, demonstrating how legal definitions are often used to suppress marginalized groups and justify state violence. These definitional inconsistencies have practical consequences for law enforcement and international cooperation. For instance, the UK’s proscription of Hezbollah in its entirety contrasts with the EU’s distinction between its military and political wings, complicating intelligence sharing and diplomatic relations (Lindahl, 2017). Similarly, the extradition of Abu Hamza to the US highlighted the friction between differing legal thresholds for terrorism charges (Fitzgerald, 2016).
3. Definitions of Terrorism Over the Years
With the rise of globalization and the interconnectedness of modern states, terrorism can no longer be viewed as a purely domestic threat. This is because attacks often have cross-border consequences, whether the perpetrators, victims, or ideologies transcend national boundaries. As a consequence, the legal definition of terrorism has grown more intricate, contentious, and politicized.
Scholars such as Alexander (1976) and Schmid (1983) have offered influential, though differing, frameworks. In order to achieve political objectives, Alexander defines terrorism as “the use of violence against random civilian targets in order to intimidate or to create general pervasive fear” (Alexander, 1976). This definition served as the basis for laws such as the 2001 USA Patriot Act, which permits domestic attackers to be classified as terrorists if their actions incite fear for political reasons, as demonstrated in the Boston Marathon bombing case of United States v. Tsarnaev (United States v. Tsarnaev, 2020). Similarly, Schmid’s definition, widely cited by the United Nations, conceptualizes terrorism as repeated violent acts committed by clandestine individuals, groups, or state actors against random targets to influence a wider audience through fear, propaganda, or coercion (Schmid, 1983). This framework influenced the European Union’s 2002 Framework Decision on Combating Terrorism, which provided the legal foundation to prosecute the 2015 Paris Attacks as terrorism under EU law.
Despite their insightfulness, both definitions are filtered via the Global North’s prevailing political and cultural prisms. They have come under heavy criticism for characterizing liberation movements, such anti-colonial movements, as terrorism while neglecting comparable state-sponsored violence (Jackson & Smyth, 2009). They also frequently neglect to take into consideration the larger sociopolitical settings in which violence takes place (Da Silva & Martini, 2021).
Progressively, the UK’s definition of terrorism is enshrined in the Terrorism Act 2000, which describes terrorism as the use or threat of action intended to influence government or intimidate the public for the purpose of advancing a political, religious, racial, or ideological cause. These actions include serious violence, damage to property, or interference with electronic systems (Terrorism Act 2000, s.1). This broad and preventive approach allows UK security agencies like MI5 and Counter Terrorism Policing to arrest individuals based on perceived intent. However, it has led to significant criticisms. For instance, critics argue that the Act blurs the line between criminality and terrorism, often targeting minority communities disproportionately (Choudhury & Fenwick, 2011).
As noted by Allchorn (2024), the British government’s proscription of National Action in 2016 and Sonnenkrieg Division in 2020 marked a shift toward recognizing far-right violence as terrorism. However, other jurisdictions treat similar groups merely as hate organizations, not terrorist threats, highlighting the inconsistencies in international enforcement. The extradition of Abu Hamza al-Masri from the UK to the US in 2012 also exposed legal tensions arising from divergent national definitions of terrorism (Rehia, 2021; Sheehan, Marquardt, & Collins, 2022).
Despite its proactive legislative approach, the UK has struggled to align its counter-terrorism laws with those of other countries. A key obstacle to international consensus is the lack of agreement on state-sponsored terrorism. For instance, as previously noted, the UK considers the entirety of Hezbollah a terrorist organization, whereas some European nations differentiate between its political and military wings (Saul, 2006). This has hindered joint operations and diplomatic cooperation. Additionally, the failure to finalize the Comprehensive Convention on International Terrorism (CCIT), an initiative under UN auspices illustrates how political disagreements continue to derail efforts at global standardization (Perera, 2020). Disputes over whether violent acts committed by liberation movements should be included in the definition remain unresolved (Müller, 2020).
The implications of broad terrorism definitions go beyond legal enforcement given that they shape public perceptions and exacerbate social division. After the 7/7 London bombings of 2005, political narratives and media coverage disproportionately associated terrorism with Islam. This framing contributed to the rise of Islamophobia and justified expanded surveillance of Muslim communities under programs like Prevent. According to the UK Home Office (2021), 70% of Prevent referrals in 2020 related to concerns about Islamist extremism, even as far-right extremism demonstrated significant growth. A Hope Not Hate (2021) report found that British Muslims were five times more likely than other groups to be referred to counter-terror programs, confirming longstanding concerns about racial profiling and discriminatory enforcement. At the same time, law enforcement responses to far-right violence have been inconsistent. The 2017 Finsbury Park Mosque attack, which resulted in one death and several injuries, was initially not labeled a terrorist attack by some media outlets, despite meeting the UK’s legal threshold. These double standards in classification and media narrative further erode public trust and foster resentment among minority communities.
4. The Challenges of Defining Terrorism in the International Community as Well as the United Kingdom
Over the years, efforts by the international community to arrive at a comprehensive and universally accepted legal definition have consistently failed, largely due to geopolitical tensions, definitional ambiguities, and clashing interpretations of legitimate violence.
According to Saul (2006), the 1937 League of Nations Convention for the Prevention and Punishment of Terrorism was the first international attempt to define terrorism. Although it was never implemented, it served as a foundation for subsequent treaties. It defined terrorism as “criminal acts directed against a state and intended to create a state of terror”. Even though the International Criminal Court (ICC) was only created in 2002, debates about prosecuting people for crimes related to terrorism had begun to take shape as early as 1973, reflecting growing concerns about violence with political motivations.
Also, the United Nations General Assembly (UNGA) has made significant attempts to address terrorism, notably through its 1994 Declaration on Measures to Eliminate International Terrorism. The declaration condemned all politically motivated violent acts against civilians as “in any circumstance unjustifiable”, regardless of ideological justification (UNGA, 1994). However, this framing raised concerns that acts of resistance against colonialism or in pursuit of self-determination such as those undertaken by liberation movements could be mischaracterized as terrorism. Such political tensions have repeatedly stalled progress on the CCIT, which remains unratified due to disagreements over how to treat state violence and freedom fighters.
In practice, international instruments such as the EU 2002 Framework Decision on Combating Terrorism and the International Convention for the Suppression of the Financing of Terrorism in 1999. adopt action-based definitions that focus on violent methods rather than the actor’s intent or identity. This results in divergent applications across jurisdictions and complicates enforcement and cooperation.
In contrast to the stalled international efforts, the United Kingdom has adopted a proactive domestic approach. Notably, the UK’s Prevention of Terrorism (Temporary Provisions) Act 1974 emerged in response to the IRA’s bombing campaigns, as already established, allowing for extensive police powers, including arrest without charge, and became a foundational moment in British counter-terrorism law (Walker, 2006).
The legal framework was also consolidated in the Terrorism Act 2000, which remains a cornerstone of the UK’s approach. This broad, action-based definition enables law enforcement to act preemptively, including on the basis of suspected intentions. The Counter-Terrorism and Border Security Act 2019 and the Counter-Terrorism and Sentencing Act 2021 further expanded this framework, incorporating offences such as viewing terrorist content online or expressing support for banned organisations. While these expansions aim to modernize counter-terror strategies, they raise critical questions about scope and proportionality especially where minor or non-violent acts fall under terrorism statutes.
One major challenge with the UK’s framework is its inclusion of “terrorist connections” in ordinary criminal activities. For example, property damage during protests can be classified as terrorism if interpreted as an act of intimidation or ideological coercion. This has led to concerns about the conflation of civil disobedience with terrorism, particularly in cases involving environmental activists and minority-led political movements (Choudhury & Fenwick, 2011).
The absence of clear boundaries between political dissent and terrorist activity risks delegitimizing social movements. The government’s Prevent Strategy intended to stop radicalization has been criticized for disproportionately targeting Muslim communities. In 2020, 70% of Prevent referrals were for Islamist extremism, despite data indicating a rise in far-right radicalization (Home Office, 2021). This approach has fostered distrust and reinforced the perception that terrorism laws serve political and racial profiling agendas.
Case law reflects this inconsistency. In R v. Gul [2013] UKSC 64, the Supreme Court upheld that even non-violent activities, such as filming insurgent attacks abroad, could be interpreted as terrorism under UK law, provided they aim to influence government policy. While the ruling confirmed the broad reach of UK law, it also blurred the line between journalistic inquiry and criminal intent.
Additionally, the UK’s expansive definition often conflicts with other legal systems. For example, its proscription of Hezbollah in its entirety contrasts with the European Union’s distinction between Hezbollah’s political and military arms. These inconsistencies hinder intelligence-sharing and joint enforcement operations. Similarly, the extradition of Abu Hamza al-Masri to the United States in 2012 took years to resolve, in part due to differing standards of evidence and variations in what each jurisdiction considered “support for terrorism”. The UK’s reluctance to repatriate British citizens who joined ISIS further reflects the tensions created by differing legal interpretations, particularly regarding citizenship revocation and evidence admissibility (Wood, 2015).
Progressively, efforts to define terrorism must balance legal clarity with respect for political context and human rights. While violence is a common denominator in most definitions, the purpose, targets, and socio-political environment should inform legal frameworks. According to Macnish (2014), this is particularly important when definitions are used to justify surveillance, proscription, or military intervention.
For international cooperation to be effective, a standardized legal baseline must be established, one that distinguishes between criminality, terrorism, and political resistance. The international community should prioritize the finalization of the CCIT, with safeguards to prevent the misuse of terrorism definitions against minority groups or freedom movements. Independent international oversight bodies could further ensure that counter-terrorism measures respect civil liberties while maintaining national security.
5. Conclusion
In conclusion, terrorism has long challenged governments and political institutions, shaping both domestic and international legal responses to violence aimed at destabilizing state authority. Despite its frequent invocation in legal and political discourse, a universally accepted definition of terrorism remains elusive. The persistent failure to achieve consensus underscores the complexities involved in defining a term that is politically loaded, socially constructed, and often selectively applied. The imposition of a uniform, inflexible definition risks marginalizing genuine expressions of political dissent, while simultaneously granting states the capacity to manipulate anti-terrorism frameworks for political objectives. Conversely, the absence of a clear definition undermines international cooperation, creates enforcement gaps, and contributes to inconsistent treatment of extremist threats across jurisdictions.
A coherent, standardized definition of terrorism is urgently needed, one that is legally precise, politically neutral, and grounded in universally accepted principles of human rights and rule of law. Such a definition should focus on acts of violence or threats directed at civilians or public institutions with the intent to advance political, ideological, or religious objectives, while distinguishing these from legitimate struggles for self-determination and civil protest. The CCIT must be revitalized as a global priority. Its adoption would provide a foundational legal framework that aligns national legislation with international norms. In parallel, domestic laws should be harmonized to enable consistent prosecution, extradition, and intelligence sharing, while avoiding overreach that infringes on civil liberties.
To ensure fair and effective enforcement, governments should establish joint counter-terrorism task forces, invest in transparent intelligence coordination, and adopt standard watchlist protocols. Crucially, this definition must apply to all extremist threats, whether Islamist, far-right, separatist, or otherwise, to prevent the politicization of anti-terror measures.
Finally, the international community should convene regular counter-terrorism summits, bringing together governments, legal scholars, human rights bodies, and civil society organizations. These forums would serve as platforms to review enforcement practices, promote accountability, and safeguard fundamental freedoms while strengthening global security.
Only through unified, balanced, and inclusive efforts can the global community confront terrorism without compromising justice, equality, and human dignity.