Limits on the Treaty Power
From Harvard Law Review:
During Justice Sotomayor's Senate Judiciary Committee confirmation hearing, she rightly stated that "American law does not permit the use of foreign law or international law to interpret the Constitution." But she also correctly recognized that some U.S. laws rely upon certain international law sources. For instance, the Alien Tort Statute "allows federal courts to recognize certain causes of action based on sufficiently definite norms of international law."
Treaties are probably the most prevalent mechanism by which domestic law adopts international law. A treaty is "primarily a compact between independent nations." Article II, Section 2 of the Constitution gives the President the power "to make Treaties, provided two thirds of the Senators present concur." And the Supremacy Clause provides that "treaties," like statutes, count as "the supreme law of the land." Some treaties "automatically have effect as domestic law" — these are called self-executing treaties. Other treaties "constitute international law commitments," but they "do not by themselves function as binding federal law" — these are called non-self-executing treaties.
Because treaties are the supreme law of the land, they could potentially become a vehicle for the federal government either to give away power to international actors or to accumulate power otherwise reserved for the states or individuals. Either possibility can be prevented if sufficient limits are placed on the federal government's authority to make and implement treaties. Some treaties, like the Arms Trade Treaty, the United Nations Convention on the Law of the Sea, and the Convention on the Rights of Persons with Disabilities, purport to let international actors set policy in areas already regulated by the federal government. These and other treaties could be used to infringe on state sovereignty. Many commentators are chomping at the bit for the federal government to make or implement treaties as a way of enacting laws that the Supreme Court has otherwise held as exceeding the federal government's powers. As Professor Nicholas Rosenkranz noted, scholars have even suggested that the International Covenant on Civil and Political Rights could resuscitate the Religious Freedom Restoration Act partially invalidated in City of Boerne v. Flores or the Violence Against Women Act partially invalidated in United States v. Morrison.
With treaties potentially supplanting federal and state governmental authority, the President and Senate should carefully scrutinize all treaties, as a policy matter. We must jealously guard the separation of powers and state sovereignty if we are to preserve the constitutional structure our Framers gave us.