Debate about the relationship between terrorist acts, counter-terrorist action and the law of armed conflict has generated more heat than light since the September 11 terrorist attacks on America in 2001. Much confusion stems from the misapplication of one word: "war".

William Taft, legal adviser to the US secretary of state, for example, recently asserted that in the fight against terrorism, a state of war is a given. He suggested, therefore, that those detained in the framework of this "war" by the US at Guantanamo Bay in Cuba fell under the law of armed conflict.

But it is a stretch to suggest that recognition of America's right to defend itself against the perpetrators of the September 11 attacks amounts to acceptance of a "war paradigm" for everyone and everything considered terrorist. Simply put, suspected terrorists captured in connection with that which is truly armed conflict - the legal term for war - may be detained under the international law of armed conflict, also known as international humanitarian law. Otherwise, they are subject to other applicable laws, such as domestic and international criminal and human rights laws, which generally prohibit detention without charges and guarantee rights to counsel and fair trials.

What, then, do we mean by "armed conflict"? The term is not directly defined in the Geneva Conventions, the internationally agreed rules of warfare, but is generally understood to involve the use of force between two or more states (international armed conflict) or a certain threshold of violence between a state and armed groups, or between armed groups within a state (non- international armed conflict).

What does this mean in relation to terrorism? The official US view is that an international armed conflict is under way, spanning the world and pitting certain countries against terrorists. This conflict will end once terrorism is defeated. In the meantime, the laws of armed conflict prevail over the entire planet - meaning that, within limits, killing, destruction of property and detentions are permitted, all without the restraint of judicial intervention. In this world, instead of merely arresting a suspected terrorist on the street, the US, if it considered him an "enemy combatant", would be within its rights to shoot him.

This theory wreaks havoc with a finely tuned and time-honoured balance between the law of armed conflict, human rights and criminal laws, and thus poses grave risks and consequences for human rights and security.

The principle that in armed conflict people may be detained without recourse to lawyers and courts is being misapplied by the US. For example, there are two categories of detainees in Guantanamo for whom long-term detention without any judicial or administrative review is not permitted by international law. First are those lawfully captured in the post-September 11 international armed conflict in Afghanistan, which ended with the installation of the Karzai government in June 2002. To the extent that hostilities continue, they amount either to an internal armed conflict or to something less than armed conflict altogether. Either way, these detainees are entitled to an individualised procedure to challenge the basis of their detention. It is ironic that the US correctly claims a right under the laws of war to detain certain people for the duration of an armed conflict, but then shirks its obligation under the very same laws to provide them with a hearing.

Second are those taken prisoner in far-flung places such as Zambia who are suspected of terrorist criminal activity, but beyond any connection with armed conflict, and are "rendered" into US custody without legal process. To subject them to the rules of detention in war contradicts both the letter and spirit of international law. People who commit hostile acts against US interests may be criminals, but are not necessarily enemy combatants. Those who commit hostile acts in the context of armed conflict may be enemy combatants, but are not necessarily criminals. Only those who commit hostile acts in the context of armed conflict but are not regular soldiers, or "privileged" combatants, can properly be considered "unlawful" or "unprivileged" combatants. While they may be prosecuted for unlawful acts of belligerence, such people, despite US assertions to the contrary, may not be denied protections of the law of armed conflict and other applicable laws.

These distinctions are not mere legal nuances. People's lives and the integrity of the rule of law hang in the balance. For this reason, the International Committee of the Red Cross has persistently asserted the obligation of the US to invoke procedures required by the Geneva Conventions to determine the status of detainees in Guantanamo and other locations, known or undisclosed.

The US is proceeding with plans to subject prisoners to military commission trials, citing the Geneva Convention provision that prisoners of war be tried by military courts. How can it do so while maintaining that no detainees are entitled to PoW status? That aside, the US risks throwing into the military-trial pot people whose alleged crimes have no connection with armed conflict, as understood in international humanitarian law. Such people can and should face trial, but not by military courts.

The law of armed conflict strikes a proper balance between the interests of state security and protection of people in times of armed conflict. Where terrorism and the battle against it amount to armed conflict, the law of armed conflict must be applied. But when aspects of the "war on terror" do not fit within the definition of armed conflict, it is in everyone's interest that domestic and international law is respected.

The writer is legal adviser to the International Committee of the Red Cross in Geneva