The Supreme Court in Missouri v. Holland famously held that Congress has the power to pass a law to implement a treaty even if the law would not fall within Congress’ legislative power in the absence of the treaty. Essential to this holding were two distinct propositions. The first proposition is that the treaty-makers have the constitutional power to make treaties on matters falling outside Congress’ enumerated powers. The second is that, if the treaty-makers make such a treaty and the treaty is not self-executing, the Necessary and Proper Clause gives Congress the power to implement such a treaty through a statute even if, in the absence of the treaty, the statute would be beyond Congress’s legislative power. The Court in Missouri v. Holl...