legitimacy

John O'Sullivan of the Hudson Institute, in an extended essay reviewing Francis Fukuyama's  After the Neocons: America at the Crossroads, makes an important point.

According to O'Sullivan, Fukuyama identifies four main currents of neocon thought: the significance of a nation’s internal regime; the risks of social engineering; that the United States, almost uniquely among great powers, can be trusted to use its strength for moral purposes; and that international institutions cannot be trusted to safeguard security and justice.

Especially problematic is the notion of international legitimacy. As Fukuyama pointed out in 2002, Europeans see legitimacy as something “handed downwards from a willowy, disembodied international level rather than handed upwards,” as Americans do, “from concrete, legitimate democratic publics on a nation-state level.”

His preference then was for the American view since the European one liberated its elites (and by extension international agencies) to follow their own preferences under the guise of pursuing common international values. In After the Neocons, however, he seems to have changed his mind: “Although international co-operation will have to be based on sovereign states for the foreseeable future, shared ideas of legitimacy and human rights will weaken objections that the United States should not be accountable to regimes that are not themselves accountable.”

This is the single most substantial rejection of neoconservative ideas in the book.

"Doubtful Dove", Financial Times Magazine, 1 April

Update (in response to a comment): 
Most Europeans would agree that the state derives its legitimacy from democratic practices and therefore that its  laws should be obeyed. Europeans would go further however an argue that the US government should be constrained by international law in not invading other countries without UN authorisation, in recognizing the ICC etc.

What you are arguing is the American view, as exemplified by the neocons. As an example of the sort of argument we get in Europe, here is one of the more sensible responses to the Euston Manifesto, Will Hutton in the Observer :

Democracy and the rule of law are indivisible. Thus, without a second UN resolution and a renewal of the mandate for intervention, the US and UK could not legally go to war and are now trying to build a democracy from a fatally flawed position. The failure of Iraqi reconstruction is not just hubris by the Pentagon and Defence Secretary Donald Rumsfeld; it goes back to the original illegitimacy of the war.

This conflates the idea of the rule of law within a democratic state with the rule of law in an international context, where it can be argued that no such democratic legitimacy obtains. Iraq is of course the case that has  provoked the most argument about the issue. No comparable bitterness was created over Kosovo, where NATO also did not have explicit UN authorisation to intervene. Perhaps this was because Clinton was in charge at that time. ('America is not the problem [...] But the Bush administration unquestionably is.' - Martin Kettle in the Guardian.)

Of course, it could have been China or Russia (we have seen what their commitment to democracy and the rule of law is in the last couple of years) that was the main obstacle to the US and UK's intervention being clearly legal. But in fact it was France. And other democratic countries, such as Chile, prevented them getting the 'moral victory' of a majority in the Security Council (but, as they say, moral victories don't count).

Iraq looms large now, but in the years to come it might be the growing economic power of China that puts the question particularly to the test. The Chinese President hot-footed it from Washington (or was it Seattle) to Saudi Arabia and then Nigeria. Where the US and the EU look to promote good governance, especially in Africa, China sees national sovereignty as paramount. It will deal with democracies, but also with whatever dictator is in power at the moment. Look at its position on Sudan / Darfur. (Listen to an interview on The World Today, after 7:05 GMT.)   

Perhaps Europe will see these issues more clearly, eventually.