This Article has not sought to argue that we are today bound to the framers' limited conception of the law of nations. The way that law develops has changed dramatically in 200 years; there is no reason to believe that the framers would not have supported an evolving definition of offenses against the law of nations. And, even if they did not, an originalist interpretation of the offenses clause is still not warranted. Nor has this Article argued that Congress has no leeway in defining offenses; its points are less strict.
When Congress determines that a certain set of actions constitutes an offense against the law of nations, it is doing more than establishing a domestic crime. It is putting its imprimatur on certain international practice and saying that that practice has reached a level at which it is binding upon nations. Congress has every reason to be especially careful before reaching such a conclusion. Obviously, if Congress bestows legal status on rules that lack the requisites of a norm--practice and opinio juris--international law suffers. It is hard enough to convince people of the reality of international law without debasing it by giving a false status to some "rules." Moreover, where the proposed norm undermines a fundamental right granted by the Constitution, Congress should be wary of codifying its transient views of international practice or the domestic practice of nations with different fundamental values. One of the ironies of Boos is that, now that many nations have begun to march to the beat of the United States' drummer, the United States in one--albeit quite small-way is arguing that it must turn around. Why Congress should deviate from a fundamental domestic norm to achieve at best a minimal foreign policy objective is totally unclear.
Determining the norms of customary international law is a complex and often indeterminate enterprise. Congress must exercise its best judgment in making that determination. But there is no reason in theory or practice for the courts to defer to Congress' determination, especially when the resulting laws conflict with the first amendment.
Charles D. Siegal,
Deference and Its Dangers: Congress' Power to "Define ... Offenses Against the Law of Nations",
21 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vjtl/vol21/iss5/1