The imperative to find terrorists and prevent their attacks requires energetic use of all the legal authorities and instruments available.
Terrorist attacks threaten more than the tragic loss of individual lives. Some terrorists hope to provoke a response that undermines the system of government. Governments must find the appropriate balance by adopting counterterrorism policies which are effective but also respect the democratic traditions of their nations.
People turn to terrorism for various reasons. Many terrorists act from political, ideological, or religious convictions. Some are simply criminals for hire. Others become terrorists because of real or perceived oppression or economic deprivation.
Resolution 1368 (echoed in 1373) of the United Nations Security Council resolved that it (not individual nations) was "determined to combat by all means threats to international peace and security caused by terrorist acts," and "expressed its readiness to take all necessary steps to respond to the terrorist attacks of 11 September 2001, and to combat all forms of terrorism, in accordance with its responsibilities under the Charter of the United Nations". This language is styled broadly, but the resolution takes pains to note the Security Council's "responsibilities under the Charter," which would allow the Security Council to authorize force only under extremely limited circumstances, and when other measures are impossible – and most likely under a U.N. flag and command. The broad array of means referred to by the Security Council also did not mention force. Instead, it ordered member countries to freeze terrorist assets, criminalize the financing and support of terrorists, exchange police information about terrorists, prevent movement of terrorists through increased border controls, and capture and prosecute terrorists.
Likewise, the resolutions do not conclude that the U.S. strikes are self-defense. Repeating language from 1368, Resolution 1373 reaffirm(ed) the inherent right of individual or collective self-defence as recognized by the Charter of the United Nations." As we shall see, this right "as recognized by the Charter" is extremely limited. Moreover, in practice the Security Council decides whether particular uses of force are self-defense only after the fact, and after careful consideration (given that, as shown below, self-defense is based on an immediate need to respond, and the response must be proportional to the threatened harm). The last of these resolutions, 1373, was issued on September 28, more than a week before the U.S. started bombing Afghanistan.
While several "professional" terrorist groups still exist and present a continued threat, the overwhelming majority of extremist groups have adopted a fragmented, leaderless structure where individuals or small groups act with autonomy. Clearly, the worst act of domestic terrorism in United States history was perpetrated by merely two individuals: Timothy McVeigh and Terry Nichols. In many cases, extremists of this sort are extremely difficult to identify until after an incident has occurred.
Combating terrorism should not be used as a pretext for discrimination against any segment of society.