In This Article Expand or collapse the "in this article" section Terrorism

  • Introduction
  • General Overviews
  • Edited Collections
  • Source Documents
  • Legal Definition
  • Use of Force
  • State Responsibility
  • International Refugee Law
  • The International Law of the Sea
  • Terrorist Financing and International Law

International Law Terrorism
Ben Saul
  • LAST REVIEWED: 23 November 2020
  • LAST MODIFIED: 23 March 2012
  • DOI: 10.1093/obo/9780199796953-0029


International law has struggled to regulate terrorism for over a century, beginning with efforts to cooperate in the extradition and prosecution of suspects, including through unsuccessful League of Nations efforts to define and criminalize terrorism as such. Until 2001 most international attention focused on transnational criminal cooperation against terrorism, through the development of method-specific “prosecute or extradite” treaties (concerning, for instance, violence against aircraft or ships, hostage taking, or attacks on diplomats) but without defining terrorism as a general concept or crime. It may, however, be possible to qualify some terrorist acts as war crimes or crimes against humanity. Since the 1970s, there were ambivalent efforts through the UN General Assembly to develop normative frameworks to confront terrorism per se, which often came unstuck on the controversial issues of “state terrorism” and liberation movement violence. Greater consensus was achieved by 1994 with the General Assembly’s adoption of a declaration against terrorism. There appears to exist an international consensus that terrorism per se is wrongful, even if disagreement remains about identifying precisely what constitutes terrorism. The effort to deal with terrorism as such suggests that the international community views terrorism as more than its underlying physical parts, which are already crimes in most national legal systems and under certain transnational treaties. The special wrongfulness of terrorism is perhaps signified by its intimidation of civilian populations, its coercion of governments or international organizations, and its political, religious, or ideological aspect. Terrorist violence has also sometimes raised certain problems under the law of armed conflict and the law on the use of force, as well as occasionally attracted sanctions imposed by the UN Security Council. Terrorism was generally dealt with, however, through the application of general legal norms rather than through the emergence of terrorism-specific rules. After the terrorist attacks of 11 September 2001, sharper international focus was brought to bear on the legal challenges presented by terrorism and counter-terrorism in numerous specialized branches of international law (particularly in the law of state responsibility, the law on the use of force, and international humanitarian law), as well as in the institutional practices of the UN Security Council and the impacts of counter-terrorism measures on international human rights law. By 2011 the UN Special Tribunal for Lebanon even declared the existence of an international customary law crime of transnational terrorism, although that decision has proven highly controversial as not supported by state practice. Efforts to negotiate a comprehensive international convention against terrorism have continued since 2000, with disagreement remaining over the scope of exceptions. There is also now increasing debate about whether a field of international anti-terrorism law is emerging.

General Overviews

There are few book-length overviews of terrorism and international law, not least because traditionally most scholars have not perceived the existence of a discrete field of international anti-terrorism law as such (Higgins 1997, Guillaume 2004), though this is changing (Moeckli 2008, Saul 2009). There are, however, various edited collections that consider how general norms of international law, including specialized branches of it, apply to the special problems presented by terrorism and counter-terrorism (Higgins 1997 and Duffy 2005) as well as (Bianchi and Naqvi 2004; Walter, et al. 2004; Ramraj, et al. 2005 and Stubbins Bates, et al. 2011 as cited in Edited Collections). Also, journal articles that explore the multi-dimensional legal issues raised by terrorism (Cassese 2001, Guillaume 2004).

  • Cassese, Antonio. “Terrorism is Also Disrupting Some Crucial Legal Categories of International Law.” European Journal of International Law 12.5 (2001): 993–1001.

    DOI: 10.1093/ejil/12.5.993

    NNNReflects on the available legal responses to terrorism in the aftermath of the 9/11 attacks, particularly the question of whether certain terrorist acts may constitute a crime against humanity, as well as the advantages of collective over unilateral action in response to terrorism under the law on the use of force.

  • Duffy, Helen. The “War on Terror” and the Framework of International Law. Cambridge, UK: Cambridge University Press, 2005.

    DOI: 10.1017/CBO9780511493959

    NNNThis largely descriptive book covers the principal international legal frameworks that apply to terrorism and counter-terrorist responses, with an emphasis on post-9/11 practice. It includes coverage of issues of state responsibility, the law on the use of force, international humanitarian law, UN responses, human rights law, and remedies.

  • Guillaume, Gilbert. “Terrorism and International Law.” International and Comparative Law Quarterly 53.3 (2004): 537–548.

    NNNCharting evolving understandings of terrorism over time, including in 20th-century anti-terrorism treaties, this article considers the possible elements of a definition of terrorism. It concludes that no universal definition exists and suggests how states may use the law of state responsibility and the law of use of force to combat terrorism.

  • Higgins, Rosalyn. “The General International Law of Terrorism.” In Terrorism and International Law. Edited by Rosalyn Higgins and M. Flory, 13. London: Routledge, 1997.

    DOI: 10.4324/9780203429365

    NNNAmong the most influential jurisprudential analyses of terrorism and international law prior to 9/11. It argues that terrorism has usually been dealt with by recourse to general norms and institutions of international law, without a demonstrable need for new terrorism-specific rules or responses—despite efforts to define it.

  • Moeckli, Daniel “The Emergence of Terrorism as a Distinct Category of International Law.” Texas International Law Journal 44.2 (2008): 157–183.

    NNNAsserts that a “special regime” of punitive international anti-terrorism law emerged after 9/11, principally due to political pressure from powerful states. The focus is more on the reasons for its emergence rather than on establishing its existence or what constitutes a “special regime.”

  • Saul, Ben. “The Emerging International Law of Terrorism.” Indian Yearbook of International Law and Policy (2009): 163–192.

    NNNArgues that there is no coherent “international law of terrorism.” Rather, there exists a plurality of responses: method-specific rules; new international law against terrorist financing; emerging general criminal rules; and the clarification of general norms in the law on the use of force, humanitarian law, and human rights.

back to top

Users without a subscription are not able to see the full content on this page. Please subscribe or login.

How to Subscribe

Oxford Bibliographies Online is available by subscription and perpetual access to institutions. For more information or to contact an Oxford Sales Representative click here.