In 2002 the Bush administration received a lot of heat for its flexible understanding of the imminence requirement of the self-defense doctrine in international law in connection with modern terrorism. Here is the 2002 National Security Strategy:
For centuries, international law recognized that nations need not suffer an attack before they can lawfully take action to defend themselves against forces that present an imminent danger of attack. Legal scholars and international jurists often conditioned the legitimacy of preemption on the existence of an imminent threat—most often a visible mobilization of armies, navies, and air forces preparing to attack.
We must adapt the concept of imminent threat to the capabilities and objectives of today’s adversaries. Rogue states and terrorists do not seek to attack us using conventional means. They know such attacks would fail. Instead, they rely on acts of terror and, potentially, the use of weapons of mass destruction—weapons that can be easily concealed, delivered covertly, and used without warning. . . .
The United States has long maintained the option of preemptive actions to counter a sufficient threat to our national security. The greater the threat, the greater is the risk of inaction— and the more compelling the case for taking anticipatory action to defend ourselves, even if uncertainty remains as to the time and place of the enemy’s attack.
Here is what John Brennan said on Friday about the same issue:
We are finding increasing recognition in the international community that a more flexible understanding of “imminence” may be appropriate when dealing with terrorist groups, in part because threats posed by non-state actors do not present themselves in the ways that evidenced imminence in more traditional conflicts. After all, al-Qa’ida does not follow a traditional command structure, wear uniforms, carry its arms openly, or mass its troops at the borders of the nations it attacks. Nonetheless, it possesses the demonstrated capability to strike with little notice and cause significant civilian or military casualties. Over time, an increasing number of our international counterterrorism partners have begun to recognize that the traditional conception of what constitutes an “imminent” attack should be broadened in light of the modern-day capabilities, techniques, and technological innovations of terrorist organizations.
Yet another example where the Obama administration (and, it seems, the international community) came around to a crazy Bush administration view.