Iran tests missile, Israel within range

This is a very difficult problem for the USA.
The real issue here is whether, since Iran has declared a desire to destroy Israel and now has the nuclear weapons to do so, Israel is justified in making a preemptive strike on Iran’s WMD capability.

If Israel is prepared to act alone and handle the consequences then I would not argue about its right to take appropriate action. But is it? I would guess that the USA is not willing to perform the strike itself on behalf of Israel. Presumably the recent meeting between the PM and President was about securing USA support, at a logistic level at least, in a war with Iran.

The right to a preemptive strike in the case of a real and imminent threat has been the subject of much debate in international law circles since the Bush Administration proposed it.

It could be argued that there is an unwritten UN convention allowing the member Nations of the Security to do as they wish in making war but other lesser countries do not have similar rights.
Quote from that reference
Those few who have sat in on the closed discussions of the Security Council, the home of peace and security, will have witnessed a body dedicated to the self-interest of the same member states that dominated the original Charter discussion. These “suits” represent leaders, regimes if you will, willing to use any resort, cook any deal, bribe by any means, undertake any violence necessary to obtain their ends. These are the same nation states that created the twin concepts of veto power and permanent seating — representing total control. This is the raw power that has corrupted the working of the Council and its mandate. It produces decisions that when implemented can run counter to the very purposes and principles of the UN itself as set out in Articles 1 and 2. These are the member states that talk of democracy and freedom, but chose to dominate the UN via their own joint dictatorship, excluding the General Assembly of some 190 member states. In order words, those states that most often bear the brunt of dishonest Council resolutions are not involved in the decision making. I refer to decision making by the five bully-boys, the results of which are often incompatible with the spirit of the Charter.

The Bush crew They had to propose a preemptive strike remit because there was no explicit provision for it.

This paper from the Center for Defense Information shows how they went about rationalizing the case for what they prefer to use the euphemism “Anticipatory Self Defense”.
It does not look like a bad argument to me and I will try to show some choice quotes.
Some commentators have suggested that WMD, and WMD proliferation, might be carved out as a special category under anticipatory self-defense. They argue that the right implied by anticipatory self-defense to act against a threat before it is “too late” may require setting a threshold in the context of WMD at some earlier point in the proliferation process, with that earlier point serving as the equivalent of the imminence of a threat. Such a point, it is argued, could represent the presence of a danger justifying a “defensive” first-strike, perhaps when accompanied by other factors such as a history of aggression, ties to terrorism, or certain criminal activities by the target regime.
and
In the past, Bush has been somewhat reserved with respect to his own presentation of a preemption doctrine, and his decision to lead a multilateral coalition against Saddam Hussein was presented with a tapestry of arguments among which were references to Security Council resolutions, the ongoing situation since the previous Gulf War, Saddam’s ties to terrorists, and humanitarian concerns. Secretary of State Colin Powell also has adopted a multifaceted and internationalist approach, and recently articulated a view of preemption that was closely akin to traditional anticipatory self-defense, referring to taking action when “see[ing] … a danger coming at you ….” Vice President Dick Cheney until recently adopted a more aggressive posture reminiscent of a Cold War ideology - “us good, them bad” - and the United States needing an unfettered capacity to take action anywhere at any time.
Since the drafting of this article, President George W. Bush delivered his London address of Nov. 19, 2003, in which he refrained from openly rearticulating a policy of preemption but did, in his second “pillar,” voice the need for free nations to be willing as a last resort to use force to restrain “aggression and evil.” While force employed in response to “aggression” could fall into the category of defense against an actual attack, using force to restrain “evil” seems a somewhat more nebulous concept, and Bush did not elaborate as to timing and circumstance. By referring to “free nations” in the plural, Bush did seem to continue a theme of multilateral action.

Given that the USA cannot afford another war right now, this should be a question for all Americans.