Congress's Treaty-Implementing Power in Historical Practice

Historical practice strongly influences constitutional interpretation in foreign affairs law, including most questions relating to the treaty power. Yet it is strikingly absent from the debate presently pending before the U.S. Supreme Court over whether Congress can pass legislation implementing U.S. treaties under the Necessary and Proper Clause, even if this legislation would otherwise lie outside its enumerated powers. Drawing on previously unexplored sources, this piece considers the historical roots of Congress’s power to implement U.S. treaties between the Founding and the seminal case of Missouri v. Holland in 1920. It shows that time after time, members of Congress relied on the Necessary and Proper Clause in passing legislation implementing treaties. Notably, both opponents and supporters of a strong treaty power accepted Congress’s power to implement treaties under the Necessary and Proper Clause, even though they did so for quite different reasons. This consensus helped lead to the growing practice of treaty non-self-execution, a practice that in turn has led Congress to play an increased role in treaty implementation. The historical practice revealed in this piece supports the conclusion that Congress has the power to pass legislation implementing treaties under the Necessary and Proper Clause, even where no other Article I power underlies this legislation.