Individual agents can't be trusted to refrain from harming others. That's why we need a state, police force, etc. But not just any old political authority will do. After all, those individuals won't suddenly become any more trustworthy once you grant them dictatorial powers. Quite the opposite! So we set up a constitutional democracy instead, with checks and balances, which limits the political power of individual agents. Now: how much of this story applies also to international relations? Are nations self-interested and untrustworthy "agents" the same way that individuals are? They sure behave like it!
It's a familiar enough analogy. We need international legal procedures for all the same reasons we need intra-national ones. And again, investing one agent (e.g. the U.S.) with dictatorial powers is no better an idea in the case of nations than it is for individuals. Unilateralism (read: vigilantism) is a recipe for disaster, as the history of western interventionism makes clear. We desperately need to establish just and effective international institutions instead. Everyone knows that the state of nature is a nightmare, so let's construct a social contract already.
Of course, not just any old system of "democratic" aggregation will do. A tyranny of the majority is no less tyrannical for that. And when multilateral decisions are based on the "bargaining" paradigm, existing inequalities in bargaining power will lead to bullying, exploitation, and unjust outcomes. We should instead aim for the ideal of the "deliberative" paradigm, in which agents reason together in pursuit of the common good. It may sound naively idealistic, but I don't think that's necessarily so. People tend to conform to norms that are considered appropriate in their social context, and that includes deliberative contexts where the norms require one's proposals to be backed by publicly justifiable reasons, rather than unprincipled appeals to special interests or the sheer assertion of one's preferences.
I think those norms are sadly quite weak at present, and one of the most important political challenges facing us today is to strengthen deliberative norms and the public sphere. There sure is plenty of room for improvement. But I do think progress here is possible, and -- if enough of us work at it -- may soon be actual. I look forward to the day when corrupt (i.e. biased, unreasonable, intellectually dishonest, or intentionally partial) political agents are treated like pedophiles, universally denounced, with common folk recoiling from their moral leprosy in disgust. Is this dream really so implausible?
It's worth noting: the corruption of our political leaders causes harm to more children than their [presumably counterfactual] pedophilia ever could. Just think how many lives would be saved if our political process was more impartial and rational. Think of the hundreds of thousands of deaths caused by the Bush Administration's bungling efforts. (It's probably millions once you factor in the opportunity costs.) Isn't that worth getting emotional about? Doesn't it show that we should care about political vices no less -- and arguably much more -- than private ones? (I don't mean to trivialize the horror of the latter, of course. Rather, I wish people would also appreciate the full horror of the former!) It would only require a glimpse of this for people's attitudes to change, for a "zero tolerance" anti-corruption political culture to develop. It could happen. I remain optimistic.
Back to the question of nations as agents. It's curious how many right-wingers are unapologetic unilateralists about foreign policy. Of course, some right-wingers are unapologetic authoritarians generally. But not all, so what of the others? For the principled libertarian or old-style conservative who trusts constitutional constraints more than an unbounded executive, why are they not so concerned about the very same executive exercising unbounded power on the international stage?
A legitimate reason here demands a disanalogy between individual and national agency. (I assume that a simple lack of concern for foreigners does not count as a legitimate basis for the differing conclusions!) But what could this be?
Perhaps democratic states are supposed to be inherently more trustworthy, because they already incorporate a vast range of perspectives, interests, and so forth, developed rationally through the deliberative norms described above. But foreign policy is not determined through democratic deliberation. Perhaps if it were then democratic states would be more reliably ethical agents. But as things stand, history surely shows that even the so-called "good guys" (Western governments) can't be trusted.
Perhaps the difference is not that an international social contract is less needed, but that it is less viable. The United Nations is certainly far from ideal. But surely it could be reformed in ways that make it less corrupt, more effective and responsive to reasons? Are there grounds for thinking that this cannot be done, or that the global level is essentially harder to govern than the national level? The greater diversity might be a problem, if it reduces the common ground that is essential for developing cooperation. But I wouldn't have thought it completely hopeless.
What else am I missing here?