The problem we face from a domestic law perspective is that to the extent Congress authorized the use of military force, it is controlling on the U.S. courts. In U.S. law, domestic legislation is to be interpreted in a manner consistent with international obligations absent an express or clearly implied intent on the part of Congress to violate an international norm. If this intent exists, the court applies the later-in-time legislation even if the result is a violation of international law. While I reserve the right to nit pick the opinion later, the court appears to have done an admirable job in reconciling all of this.

When Congress authorized the use of military force against a global “organization,” this conflict with domestic, IHL and human rights law (to the extent which it applies, which you must agree is a heavily debated issue) was bound to occur. As we have earlier discussed, in U.S. law the President has implied powers based in military necessity to carry out such authorization. It is impossible to reconcile your view of the territorial scope of the IHL of NIAC with the authority provided by Congress. I am far less convinced than you are that the territorial scope of this IHL is limited to Afghanistan, but reserve judgment on its true scope as a matter of customary IHL. The laws of war were functional, not territorial, at their origins. They regulated the “belligerent intercourse” of contending parties to an armed conflict wherever those hostilities occurred, and still do to a large extent.

While legislation on various aspects of these powers is preferable, it absence is not fatal in U.S. law. The Lieber Code governing the conduct of Union troops in the U.S. Civil War, including the punishment of the enemy, the detention and punishment of enemy fighters and civilians, the exercise of martial law, etc. was entirely executive in nature. (For its time, it was also an improvement over the absence of “law” governing internal conflict.) I assume that this is a truly astonishing concept for any lawyer raised in the civil law tradition, and is even difficult for U.S. lawyers who do not understand our ever-dwindling common law traditions. Nevertheless, this condition is preserved in U.S. law on the topic in the form of Supreme Court precedent and, to a limited extent, some broad statutory provisions.

Congress could certainly correct all of this with legislation. Its failure to do so (but for a few issues on detainee treatment and prosecution) is conspicuous.