Since September 11, 2001, terrorism has emerged as the biggest
security concern across much of the world. It has also become a kind of talisman whose invocation seems to absolve those fighting against it from previously unchallengeable legal and moral restraints. The use of terrorist tactics of unprecedented destructiveness by al-Qaeda and a network of associated groups is a frontal assault on the values of humanitarian law, and has at the same time created a crisis within the law, undermining acceptance of its core principles by the world’s pre-eminent military power.

Al-Qaeda declared war on America long before 9/11. It was in August 1996 that Osama bin Laden first proclaimed a jihad against “the Americans occupying the land of the two holy places.” “I’m declaring war on the United States,” he confirmed to an interviewer from ABC News two years later. In one respect there was nothing surprising in this choice of language. Armed groups labelled as terrorists by the States against which they fight have regularly aspired to the status of warriors engaged in a legitimate contest and sought to dignify their campaigns of violence with military trappings. However in this case al-Qaeda was able to muster the resources and organizational skill to bring off an attack whose impact was on a scale similar to interstate conflict, half a world away from the group’s base.

The suicide hijack-bombings of September 11 killed close to 3,000 people, brought down the tallest buildings in New York and inflicted serious damage on the Pentagon. The United Nations Security Council implicitly, and NATO explicitly, characterized them as an armed attack that gave the United States a right of self-defense under the UN Charter. Within a day, President Bush had announced a “war on terrorism” that he later said would be fought “wherever terrorists hide, or run, or plan.” This conflict, according to a subsequent White House directive, ushered in a new paradigm that required new thinking in the law of war.

Terrorism is a concept that does not have a recognized and agreed legal meaning. Because the word is not merely descriptive but normative, it tends to become a place-holder for those forms of political violence that the speaker regards as most illegitimate. The most authoritative recent definition is in the 2004 Report of the UN High-Level Panel on Threats, Challenges and Change, which refers to terrorism as “any action… that is intended to cause death or serious bodily harm to civilians or noncombatants, when the purpose of such an act, 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.” This statement dismisses the idea that attacks on civilians may be raised above the level of terrorism if they take place as part of a campaign of resistance to occupation. However it also excludes attacks against military targets by non-State groups (such as al-Qaeda’s attack on the American destroyer Cole in Yemen in 2000) from the sphere of terrorism and so would be regarded as incomplete by some people.

The UN Panel proposed its definition as the basis for a comprehensive international convention banning terrorism—something that has long been under discussion at the United Nations—but the idea was not endorsed by the 2005 UN World Summit, as some developing countries insisted on preserving an exclusion clause for national liberation movements. Nevertheless, the actions associated with terrorism are already prohibited under a wide variety of international and domestic laws. Acts of terror when committed by non-State groups are generally crimes under the law of the country where they take place, and are most often prosecuted as such. For instance, Ramzi Yousef, who masterminded the 1993 bombing of the World Trade Center, was convicted in a New York court and sentenced to life imprisonment without parole. In addition, in recent decades, there have been 13 international conventions directed at specific acts identified with terrorism, including the 1979 Convention on the Taking of Hostages and the 1997 Convention against Terrorist Bombings.

Terrorist actions committed in the context of armed conflict are violations of international humanitarian law. One rule—stated in Article 51 of the first Additional Protocol of 1977 and Article 13 of the second Additional Protocol—specifically addresses the psychological effects that terrorism aims at, by prohibiting “acts or threats of violence the primary purpose of which is to spread terror among the civilian population.” This provision is a reminder that—for all the debate about whether terrorism as a concept is necessarily limited to non-State groups—national authorities and regular armed forces can also carry out acts of terror.

In addition, treaty and customary law contains rules against the deliberate targeting of civilians, the launching of indiscriminate attacks, and the taking of hostages that are binding on all participants in both international and non-international armed conflicts. The prohibition on perfidy would ban attacks that rely on the attacker using the appearance of a civilian to avoid suspicion (as with most suicide bombs). In addition, wholesale acts of violence or systematic campaigns directed against a civilian population as an organizational policy might qualify as a crime against humanity.

As a method of fighting, terrorism represents the ultimate form of asymmetrical warfare, in which an armed group tries to neutralize the greater strength of its opponent by avoiding conventional battles in open terrain. Like guerrillas, terrorists fight with stealth; indeed there is some overlap between the two categories, and groups like the FLN (Front de Libération Nationale) during the Algerian war of independence against the French in the 1950s or the Tamil Tigers today in Sri Lanka combine elements of both approaches. But terrorism, as generally understood, does not involve an attempt to capture and hold territory, or to attack military targets for anything other than symbolic purposes. For these reasons campaigns of terror that are divorced from any broader military struggle have traditionally been seen as a form of crime, not warfare.

The uniqueness of the Bush administration’s response to September 11 lay in invoking the notion of war to claim sweeping powers against al-Qaeda suspects, while at the same time denying the protection of the laws of war to America’s supposed enemies. U.S. officials argued that the traditional prerogatives of war—the right to detain hostile fighters without trial or target them without warning—were necessary and appropriate, but that the restraints embodied in the Geneva Conventions, the Additional Protocols and customary law were not applicable against such an unconventional and dishonorable foe. By their actions, al-Qaeda’s fighters had placed themselves outside the law and could be treated as military necessity required: this was the moral and legal intuition to which American policies appealed for justification.

But the administration’s position—based on arguments developed largely by civilian officials, often in the face of strong opposition from senior uniformed lawyers and State Department experts—relies on an extraordinarily narrow and anachronistic picture of international law. It may have been true in earlier centuries that irregular fighters were entirely at the mercy of their enemies, but since World War II a complex set of international rules has been developed that builds on a vision of essential human dignity to offer some fundamental protections to individuals in all circumstances. These rules are found in Common Article 3 of the 1949 Geneva Conventions, in Article 75 of the first Additional Protocol, in human rights instruments like the Convention against Torture, and in customary law. They enshrine principles of humanity and due process and are not in any way dependent on a reciprocal commitment from the individual protected by them to respect similar values himself. The decision of the U.S. Supreme Court in the Hamdan case in June 2006, ruling that Common Article 3 applied at a minimum to American military operations against al-Qaeda, recognized this point.

Whether or not the fight against them is characterized as an armed conflict, suspected terrorists are entitled to baseline protections (for instance against cruel and degrading treatment or improper trials) in all situations. What about the Bush administration’s claim that the existence of a “war against terrorism” allows the United States to target enemy combatants or detain them indefinitely? As stated, the phrase is legally meaningless, since the notion of war has historically been restricted to conflicts between States and there cannot be a war against a method of fighting. More cautious and lawyerly administration officials speak instead of an armed conflict against al-Qaeda and affiliated groups.

Even this claim is open to question. For an armed conflict to exist there must be protracted armed violence between two or more organized groups, and it is by no means clear that those conditions hold in the case of the United States and al-Qaeda (as distinct from the geographically limited conflict against the Taliban in Afghanistan that the U.S. launched in October 2001). More importantly, it is also not clear that the traditional prerogatives of warring parties—to target or detain enemy combatants—would automatically carry over into such an unconventional conflict, if it existed. Fundamental human rights principles forbidding arbitrary killing and prolonged arbitrary detention are now generally agreed to apply in time of war as well as peace. As armed conflict moves ever further from the traditional model of uniformed troops confronting each other on the field of battle, these human rights principles are likely to assume increasing importance in our understanding of what is permissible. In a conflict that may have no definite end, and where there is enormous uncertainty about who is taking part in hostilities on the other side, it does not seem compatible with these norms to seize or target anyone you assert to be an enemy combatant without independent oversight.

The Bush administration’s reluctance to acknowledge these principles has obscured the continuing relevance of international law and threatens its authority. In the long run, however, concern over the excesses of the “war on terror” may force a new awareness that the overlapping legal regimes that apply to the use of armed violence contain no gaps and operate across more of a continuous spectrum than has previously been recognized.

(See detention and interrogation, international vs. internal armed conflict.)