The first question, then, is, what is war? According to Lassa Oppenheim, one of the giants of international law, "War is a contention between two or more States through their armed forces, for the purpose of overpowering each other, and imposing such conditions of peace as the victor pleases". A terrorist attack, no matter how heinous, committed by non-state actors, is not a casus belli, an "act of war", except in a metaphorical sense. It therefore cannot justify a state resorting to war against another state in response to the attack, unless the other state’s responsibility for the attack has been unambiguously established.

But, as is clear from the statements of the President and other high officials, no such responsibility has been proved, except again in a metaphorical sense. They speak of making war against countries that "support", "tolerate" or "harbor" terrorists. Saudi Arabia refuses to this day to extradite the eleven men indicted in the 1996 attack on the Khobar Towers, in which 19 US airmen were killed and 370 injured. Does this mean that Saudi Arabia is supporting terrorists and that we are or will be at war with Saudi Arabia? A recent study by the Congressional Research Service alleges that Osama Bin Laden’s organization has bases or tentacles in 37 countries. Are we, or will we be, at war with all of them?

Nor is it possible to declare war against an unidentified enemy, which is essentially what the President and the Congress have done in the aftermath of the attacks on the Twin Towers and the Pentagon. Yet, both psychologically and legally, the use of war terminology has grave consequences. Psychologically, as shown by the WAR banner headlines in the days following September 11, it creates a mood of "follow the leader, wherever he may lead" and makes bloodthirsty monsters out of normally decent citizens. As one correspondent said in the Letters column of the New York Times on September 18, "It is not enough to wipe out Afghanistan … I will be satisfied with nothing short of a sweeping and devastating assault on all those countries that train, finance and protect those whose stated goal is the slaughter of Americans."

Legally, a state of war triggers all sorts of undesirable consequences. At the level of international law, the proclamation of a state of emergency, which is normally less than a state of war, allows a state party to the International Covenant on Civil and Political Rights, such as the United States, to "derogate" from its obligations under the Covenant in respect of several basic human rights, including freedom from forced labor, the right to bring habeas corpus proceedings, freedom of movement, equality before the law and freedom from arbitrary arrest.

A de facto, or functionally equivalent, declaration of war, followed by acts of war, naturally triggers the right of self-defense by any state affected. The Taliban has already prepared the Afghan people to fight a holy war against the United States, once the US makes good on its promise to "end" that state. Every other state against which military action is taken by the global antiterrorist coalition in the making will consider itself entitled to respond with armed force against any member of the coalition. The US, with its farflung global outposts, military and otherwise, and its long list of potential target states, is particularly vulnerable in this respect. Thus, conducting the impending – and necessary – antiterrorist operation under the banner of war legitimates the cycle of violence, which it is sure to spark.

Proceeding under a flag of war will of course also have, indeed has already had, grave consequences in terms of domestic constitutional law. While President Bush has not formally invoked the War Powers Act – Presidents hardly ever do – Congress has made it unnecessary for him to do so and has approved in advance the uncharted voyage on which he and the armed forces are about to embark.. Thus, while a few courageous members of Congress may be heard to say that the joint resolution they passed on September 14 does not give the President a blank check for any type of military operation, it does in fact do so for at least sixty days and, judging from past experience, as well as the ambiguous language of the resolution, well beyond that time. To the extent that the resolution authorizes "the use of United States armed forces" against "nations" (as well as "organizations or persons") it is a green light for war. Its only saving grace is that it is limited to the use of force against those nations, organizations or persons which the President "determines planned, authorized, committed or aided the terrorist acts that occurred on September 11, 2001." Thus it is not – not yet – an authorization to use force for the extirpation of every kind of terrorism from every part of the globe.

It remains to be seen what emergency powers the administration will seek to arrogate to itself and to what extent these will impinge on the very democratic freedoms in whose name this "war" is going to be fought.

In one respect the President has already exceeded his powers. His call for "Osama Bin Laden dead or alive" violates Section 2.11 of Executive Order 12333, which states in plain English: "No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination." No doubt the vast majority of Americans would like to see Osama bin Laden dead, but that is not the point. The point is that if the prohibition against assassination, enacted at the request of Congress in 1981 by none other than President Reagan is to be ignored, it must first be repealed by this President in consultation with this Congress. Repeal by Presidential speechwriters is not in the best American tradition and sets a most dangerous precedent.

A crime against humanity of unimaginable proportions has been committed on our territory. The perpetrators of this crime, and those who may be planning similar atrocities, must be hunted down and brought to justice with every resource of the world community – short of war. To embark on a course leading to what Thomas Friedman has already called World War III would be compounding the tragedy and giving the Osama Bin Ladens and their ilk exactly what they want: A holy war, with vastly greater numbers of innocent victims than those who suffered horrible deaths in New York and Washington on September11, and, if not the end of democracy as we know it, at least its diminution. Civil society must not allow this to happen.

Peter Weiss is President of the Lawyers Committee on Nuclear Policy and of the International Association of Lawyers Against Nuclear Arms.