Michael W. Doyle Responds

Preventing Iran from acquiring nuclear weapons is desirable. But is it vitally necessary or just desirable? Is it doable, and, if so, at what cost? Answers to those questions will explain why I think we should try to prevent, but settle for deterring.

Prevention is not a radical policy. It is fully legal when authorized by the UN Security Council under Article 39 of the Charter, which calls upon the Council to determine “threats” to international peace and decide what to do about them. The Council imposed preventive sanctions on South Africa in 1977 to punish apartheid and prevent a regional race war. In the Cuban Missile Crisis, in October 1962, the United States unilaterally—illegally but arguably justifiably—imposed a blockade to prevent the Soviet Union from making Cuba into a missile base threatening the United States. Responsible governments regularly face the choice of whether to try to deter a potential foe or to act first—that is, preventively—to save themselves from a blow that the other seems to intend, has delivered before, and could again deliver.

The international community is beginning to develop a jurisprudence of prevention focusing on lethality, likelihood, legitimacy, and legality—criteria that help assess the seriousness of threats not yet imminent and the appropriate responses to them.

• Lethality identifies the likely loss of life if the threat is not eliminated.
• Likelihood assesses the probability that the threat will occur.
• Legitimacy covers the proportionality, necessity, and deliberativeness of proposed responses.
• Legality asks whether the threatening situation is itself produced by legal or illegal actions, and whether the proposed remedy is more or less legal.

All four standards should be taken into account when considering prevention. Absent good reasons relevant to each standard, preventive action is not justified.

Preventing an Iranian bomb is clearly desirable, judging by those 4Ls, but not an immediate vital necessity. Lethality is fortunately not imminent. Iran is four to ten years away from nuclear weapons according to Director of National Intelligence John Negroponte. But there is a long-run lethal threat. Mohamed ElBaradei, head of the International Atomic Energy Agency, judges that Iran is at least seeking a “screwdriver” bomb, one that would be a week or so away from assembly in a crisis. President Mahmoud Ahmadinejad’s threats to “wipe Israel off the map” and Iran’s arming of Hezbollah clearly threaten Israel. Annual “Death to America” celebrations and the 1996 bombing of the Khobar Towers in Saudi Arabia that housed U.S. airmen convey continuing threats to the United States. Current threats may be so much hot air; but it is disturbing that, knowing how provocative they have been, Ahmadinejad has repeated them time and again.

Much more likely than a direct attack on either I...