Continued from here.

What divides the two groups in the foreign law debate? I will make a few conjectures, again with the proviso that I am supplying broad generalizations and do not mean to attribute any of these views to any particular person (including Koh) on either side of the debate.

Doctrine. Much of the debate in the academic literature has been carried out at the level of doctrine. The Bradley and Goldsmith article I mentioned in my previous post made a doctrinal argument, about what courts really do or should do; their critics took issue on these grounds. In his series of posts criticizing Koh, Ed Whelan also made doctrinal arguments. Whelan's many critics made doctrinal arguments (you can find many of their posts at the Opinio Juris blog). My view is that doctrine does not get you very far. There are too few cases, going in all directions. A dull, dispiriting, and inevitable debate about what the founders believed has gone nowhere. The passions involved tell you that more is going on than a disagreement about what the sources say.

Politics. There is a clear left/right divide, with the left favoring the foreign law position. (In academia, "right" means something like center. Outside academia, though, "right" really does mean right, far- as well as near-.) Conservatives suspect that people on the left like foreign and international law because those people believe that these bodies of law tend to be more left-wing than American law is. (Whether international/foreign law is in fact farther to the left than American law is a question best left for another day. For too many people, the rest of the world consists of Europe rather than Iran, China, or Russia.) They note that people like Koh spend a lot of time discussing European attitudes toward the death penalty but not the European laws banning political parties or the worldwide trend toward restrictions on "defamation of religion." More is going on, however. These political positions reflect broader ideological and institutional commitments.

Institutional commitments. The left and right disagree about more fundamental issues, such as constitutional interpretation; these issues are implicated by the foreign law debate. Conservatives see an attack on originalism, which leaves little room for foreign law, and what for them is the typical liberal's excessive faith in the judiciary and distrust of the executive. The pro-foreign law positions are mostly about how the courts can take an active role in promoting international law. In their darkest nightmares, conservatives see a new generation of liberal judges selectively importing liberal norms into American law by citing foreign and international law—just when the conservatives thought they were on the verge of winning the debate on originalism.

American exceptionalism. Deeper still is the question of how Americans see themselves in the world. For conservatives, America is the exceptional nation. Other states should imitate the United States, not the other way around. Conservative or not, this is also mainstream public opinion. The pro-foreign law people, like most academics, reject American exceptionalism: the United States is an ordinary nation—good in some ways, bad in others. The United States needs to be disciplined and constrained, so that it is compelled to take into account the values and interests of other people in the world. The executive and legislative branches have no incentive to do this because only Americans can vote in U.S. elections. For this reason, only the courts, with their unelected, globe-trotting judges, can put a break on American exceptionalism.

It is this last issue which has made the foreign law debate politically explosive. Liberal academics have detected in the courts occasional dim glimmerings of awareness that the United States does not treat foreigners fairly. The academics seek to nurture this little plant, but the real basis for their view is not doctrinal but cosmopolitan—the particular cosmopolitan view that the fact of one's birth on one side of a border or another is morally arbitrary. This view throws democracy itself—at the national level—into question and pulls the rug out from under one of the chief rationales for originalism and for judicial restraint—that they prevent judges from interfering with democratic outcomes. Modern democratic theorists believe that foreigners should have a say in American policy, at least to the extent that American policy affects them. Their followers in the legal academy have taken the next logical step, concluding that if the political branches will not give foreigners a vote, or at least take their views more seriously than in the past, then the courts must figure out some other way to protect foreign interests. Incorporating foreign and international law is the way to do this.

The problem for these people, and a problem that conservatives have been quick to exploit, is that cosmopolitanism has little popularity among Americans. Koh himself has resolved this dilemma simply by claiming that whatever is cosmopolitan is in America's interest—that the American and global interest converge in a standard set of Democratic party policy prescriptions. But few will be persuaded by this argument.

The foreign law position, then, is politically vulnerable, while at the same time philosophically coherent and highly appealing to liberals and indeed sophisticated people of other political stripes who dislike America's thuggish behavior on the international stage. In this way, it has a lot in common with Warren Court constitutionalism and, depending on how political winds blow, may someday likewise enjoy a moment in the sun.