The extent to which customary international law, or the law of nations, applies in the United States is the subject of continuing debate.  Does customary international law have a significant role in international and domestic law in the era of multi-lateral treaties?  Are domestic courts empowered to enforce customary international law without express legislative authorization?  When the use of customary international law is statutorily authorized (such as in the Alien Tort Statute), how is it determined?  These are just a few of the vexing problems lawyers and judges face when a litigant draws on international law in domestic litigation.

In a more subtle context, courts from time to time are confronted with the issue of how domestic laws should be interpreted in light of existing international norms.  Most visibly, this debate has focused in recent years on whether Supreme Court justices may cite foreign and international law in determining the scope and meaning of constitutional rights and provisions.  A less controversial corollary issue is the extent to which international norms shape judicial interpretation of domestic statutes.  In an age when much judicial decision-making is decried as activist law-making, the role of international law in statutory interpretation is apt to have an increasingly political as well as legal component.

One of the earliest Supreme Court cases to consider the scope of customary international law in interpreting domestic legislation was Murray v. The Charming Betsy, 6 U.S. (2 Cranch) 64 (1804), which spawned what is now known as the Charming Betsy Doctrine.  More of a rule of statutory construction than a legal doctrine, Chief Justice Marshall famously wrote that “an act of Congress ought never to be construed to violate the law of nations if any other possible construction remains.” Far from a detailed exposition on the balance of international law and domestic legal enactments, the canon of construction adopted in The Charming Betsy was succinct and non-controversial.

In the more than 200 years since The Charming Betsy put the Supreme Court’s imprimatur on this rule of construction, the international and domestic legal landscapes have changed considerably.  Curtis Bradley details this evolution in his excellent article, The Charming Betsy Canon and Separation of Powers:  Rethinking the Interpretative Role of International Law, published in the Georgetown Law Journal in 1998.  According to Professor Bradley, there are various strands of academic debate on the meaning and scope of the Charming Betsy doctrine. 

From Bradley’s perspective, the Charming Betsy doctrine is grounded in separation of powers concerns, such that unless Congress clearly expresses its intent to do so, courts will not interpret domestic statutes in a manner that would put the United States out of compliance with international norms.  The purpose of the doctrine, therefore, is to prevent courts from creating foreign relations difficulties for the United States by unnecessarily creating conflicts between domestic and international law when interpreting ambiguous statutes.  On a more general level, this view of the doctrine can also be seen as a practical method of determining legislative intent.  Courts presume that Congress intends to act in conformity with international law to avoid foreign relations problems.  A broader approach to the role of the Charming Betsy doctrine is to consider it as a mechanism to ensure the United States acts in accordance with international law.  Bradley has dubbed this the internationalist approach, whereby some scholars and courts suggest that the doctrine implies the obligation to interpret domestic statutes to conform to international norms.

Despite these divergent views on the purpose and scope of the Charming Betsy Doctrine, courts continue to cite the Restatement (Third) of Foreign Relations (1987) as a correct statement of the doctrine.  According to Section 114 of the Restatement, "[w]here fairly possible, a United States statute is to be construed as not to conflict with international law or with an international agreement with the United States."  Recently, the Ninth Circuit took up the issue of the scope of the Charming Betsy doctrine in Serra v. Lappin, 600 F.3d 1191 (2010) and found that the doctrine, as described in the Restatement, is a narrow rule to be applied in only a limited number of circumstances. 

In Lappin, the plaintiffs asserted that international norms dictated interpretation of certain provisions of federal law pertaining the prisoner employment and compensation.  The Ninth Circuit rejected this argument, finding as follows:

“The Charming Betsy canon is not an inviolable rule of general application, but a principle of interpretation that bears on a limited range of cases. Mindful that ‘Congress has the power to legislate beyond the limits posed by international law,’ . . . we do not review federal law for adherence to the law of nations with the same rigor that we apply when we must review statutes for adherence to the Constitution. We invoke the Charming Betsy canon only where conformity with the law of nations is relevant to considerations of international comity, and only ‘where it is possible to do so without distorting the statute.’" (Internal citations omitted).

In reaching this conclusion, the Ninth Circuit in Lappin appeared to endorse the separation of powers theory posited by Professor Bradley.  According to the court, the purpose of the Charming Betsy canon is to avoid the negative foreign policy implications of violating the law of nations.  Because claims by United States citizens against the United States government do not raise foreign relations concerns, the rule of interpretation has no application in purely domestic cases. 

This recent case law suggests that at least for now, the Charming Betsy doctrine may remain a rule of interpretation with somewhat limited application to cases with an international dimension that involve an ambiguous legislative enactment that may run contrary to international law.  With the growing number of international cases litigated in American courts, however, it seems certain that the reconciliation of domestic and international legal norms is a problem that will require continued development in the courts in the coming years.