From the beginning of our constitutional life, the Supreme Court has articulated principles that structure the juridical relationship between international law and domestic law. These principles purportedly offer rules of decision for resolving in domestic courts the potential in-consistencies between external and internal sources of law, and they do so with the surface simplicity of axioms. Treaties, for example, cannot trump constitutional norms.' Customary international law can provide a rule of decision at least in the absence of controlling legislative or executive acts. In the case of an irreconcilable conflict between a treaty and a statute, the latter-in-time prevails. When Congress incorporates conventional or customary norms into a statute, those norms become directly enforceable and in the absence of any other applicable principle, United States statutes should be read "where fairly possible" so as not to violate international law.
These principles have been criticized variously as innocuous, anomalous, and asymmetrical.' But they also reflect the Court's insistence hat domestic and international law be accommodated, not necessarily as equals, but as two legitimate sources of norms binding on the United States and enforceable in its courts. Doctrinal purity may have been sacrificed, but the Court's accommodationist imperative has had the advantage of avoiding both dualist and monist extremes. As a result of the Supreme Court's approach, the debate persists about the proper way to characterize the relationship between international and domestic law in the United States.
Ralph G. Steinhardt,
The Role of International Law As a Canon of Domestic Statutory Construction,
43 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol43/iss4/1