I've noticed in a variety of contexts that there are some rather well-educated, articulate individuals out there who have what seems to me to be a fanatical, quasi-religious belief in "international law", and the idea that it should trump any other conflicting consideration. In the constitutional law field, this is reflected in the argument that the president and the courts should ignore domestic law and the Constitution if they conflict with international law--even if the United States isn't a party to any binding international agreements on the particular subject at hand.
On a more personal level, I've had a few email conversations with Volokh Conspiracy readers along the following lines:
Reader: Israel is illegitimate because it violated international law by not allowing Palestinians who fled Israel during the War of Independence to return.
Me: I'm not an expert on international law [UPDATE: For the record, and in response to some of the comments below, I'm not conceding that Israel did indeed violate international law in this matter. I don't know anything about it, though comments below and an email I received cast grave doubt on the matter. But I didn't argue the point in my correspondence] but I do know something about Israeli history. There is no practical way Israel could have permitted the return of most of these refugees. First, the Palestinian and broader Arab leadership remained committed after the war to Israel's destruction. The Arab community within Israel's border had participated in the war against Israel. The immediate result of allowing hundreds of thousands of generally hostile Arabs back into Israel (which had well less than a million Jewish residents at its founding) would have been constant intercommunal violence and ultimately another war. You can't expect Israel to have committed national suicide.
Reader: International law says Israel had to do it anyway.
Me: But Israel was busy resettling hundreds of thousands of Holocaust survivors, as well as hundreds of thousands of refugees thrown out of Arab countries, many of whom had to live in tents for years. Israel simply didn't have the resources to deal with those problems and also deal with trying to resettle hundreds of thousands of hostile Arabs.
Reader: Doesn't matter, Israel was violating international law.
Me: But most of the refugees moved only a few miles from their original homes, to places where the culture and language was often indisinguishable from their hometowns. It was like moving from Brooklyn to Queens. Surely the Arab countries that had participated in the war against Israel, and had egged on the Arabs of Palestine to launch a war against the Jews, should have simply funded the resettlement of the refugees. Indeed, even the money that has gone to UNRWA over the years from the West would have more than sufficed. Instead, the Arabs preferred to use the refugees as a propaganda tool, and canon fodder, against Israel.
Reader: All well and good, but Israel was in the wrong, because it violated international law.
I'm not exaggerating when I say that I've had several correspondences along these lines, none challenging the points I raised (though not necessarily assenting, either), but simply arguing that any such points are completely irrelevant, because all that matters is whether or not Israel violated international law.
It has struck me that debating such people is just as frustrating and unproductive as arguing with a religious believer about some matter within the scope of his religious belief--just substitute "God says so" for "international law says so."
The point of this post is not to defend the points I made in my email correspondence, but to ask informed readers about when and how "international law" gained such cult-like status that well-educated people believe that merely invoking it (or their interpretation of it) is sufficient to settle even the most nuanced and contentious debates, that it should always trump domestic law, etc. Please restrict your comments to either explaining, or, if you are so inclined, defending, this phenomenon. (Or is "international law" largely invoked to try to restrain the actions of the U.S. and Israel, but largely ignored more broadly?--e.g., I haven't heard of any other nation's besides Israel's legitimacy being questioned because of past or even present real or imagined violations of international law.)