It is this: the regime of international law, that is, the framework of institutions that is meant to uphold international law, should be held in contempt by all those committed to democracy and human rights, so long as and to the extent that those institutions are merely a cover for inaction and/or connive at the most blatant criminality by states against their own peoples.
How can a citizen of any country respect a legal system which essentially stands by to the criminality of governments that have a place in the very councils whose task it is to strengthen international law? Countenancing the rape, torture and murder of Zimbabweans that system thereby countenances the rape, torture and murder of anybody, and therefore of you too. For the principle is a general one: it's not that Mugabe's thugs may destroy this man or this woman; it's that a government, a regime, may get away with killing those under its jurisdiction for all that the agencies of international law are likely to do about it. That is not a legal system to be esteemed. The publics of democratic countries also have an obligation in this regard. We should not accept, we should denounce, a system of law that accommodates such things.
Can one support the idea of a law-governed world and the development of international law to this end, while at the same time holding that system in contempt and condemning it for its failures? Indeed, one can and one should. The criticism and condemnation are for its shortcomings. In so far as the law and its implementation (where, as rarely, this occurs) live up to an acceptable ideal of the rule of law, it should be supported.
There's a lot going on here, but I will try to isolate a few points worth mentioning.
1. The status of the claim--the manner of opposition is left unclear. Is it holding a lack of esteem for international law, or holding it in contempt? This is, as one might say, the negative portion of the claim, which is supplemented by the positive claim, which is support for 'the idea of a law-governed world.' However, as is the case in so many other areas of philosophy, the negative case does not imply the positive case; Descartes thinks he has found reasons to believe in the world, in bodies, and in God, but he is one of the few who finds his reasons convincing (and if Rorty's thesis in Philosophy and the Mirror of Nature is correct, this is a structural feature of the modern mind). I see moral reasons to accept the negative premise--it may be the only morally correct conclusion to reach when one looks at international politics--but no reason to accept the positive case. Now, as I understand it, Norm deflects this criticism by reversing the priority of the two claims--because the positive belief in international law comes first, then follows the need to reject institutions that subvert that goal. I'd suggest amending the text so that "for those committed to democracy and human rights" comes first, to establish the form of the claim.*
2. The problems international law faces are deeply structural. As has often been argued, there is no central power which compels the actions of states; most instruments of international law are created by the action of a number of governments. Consequently, international law is built to serve two sets of interests: those of states, who wish to arrogate as much power back to themselves under the name of sovereignty or whatever other doctrine makes that possible, and those of international lawyers (and the concomitant portions of governments) who wish to expand the scope of international law, often for its own sake. Neither of these has democracy or human rights as a primary goal.
3. The primary reason I retain skepticism about the thesis is the invocation of 'the rule of law,' a concept that I think has done much damage to the prospects for international law. To be more correct, I believe the idea is, and has been, applied in form even while the content of international law was not prepared for it. States make international law;** states have lots of interests, not all of them good. Norm is incorrect, I aver, to think that it's 'international law and institutions' that are the problem; even on a strict positivist Doctrine of Sources, change is possible. It's the concept of rule of law that is causing the problem--to suggest that current law and institutions are doing something less than their best work, that we ought to hold them in contempt, is, to the positivist, to attempt to subvert the rule of law. Given that positivism is the dominant position within international law, and positivists can only think in terms of law, the critic must always be fighting a rearguard action--proving that they do not wish to subvert order entirely.
One might think of the domestic analogy; one need not suspend the concept of rule of law in order to protest the failure to rigorously uphold certain laws, or change them in the name of morality (think of the civil rights movement of the 50s). The analogy fails, I think, because a critique of international law as it now stands does not, I think, go far enough to ask for full application of all the laws; it needs to question the legitimacy of international institutions as such. To the extent that the institutions have failed--and in cases of severe human rights violations, their failure is the anticipated result, not an exception--then the institutions need to be replaced, and going halfway won't do it.
4. Politics, or the 'so what?' question: I get that the point of the thesis is to speak to the proper attitude and political orientation of those committed to human rights and democracy, and as one of those people, I find it to be compelling, if not yet addressing everything to the extent I would like. But there is a tremendous gap between the attitude of the individual and the function of the international system, which is an omission that, again, I think needs to be rectified. There have always been people who are committed to these things, who hold in contempt the institutions that fail to respond when needed. What makes this different, or new, or needed now in a way it hasn't been before? How does it expand beyond the attitude of one, or a number, or even a handful of states?
*I am not convinced 'democracy and human rights' is the correct formulation; depending on how one reads the source doctrine of international law, one could well argue that we have the institutions we do precisely because the international law is democratic. Additionally, Norm (I think) supports the priority of human rights to democracy--if we can only have one, it's better to have the human rights. Otherwise, the thesis collapses, on the condition that a system condoning violations of human rights is just what states want.
**A few international lawyers will argue for doctrines that are exceptions to this rule: the 'erga omnes' obligation, or else the concept that international law 'solidifies' after a treaty is signed and confers binding obligations not just on the signatories, but on everyone. These concepts are not without their own difficulties, and are primarily used by positivists, as a way of not needing to appeal to morality to frame international law. Thus I think Norm would not want to employ them.