How much deference should courts afford the executive’s interpretations of statutes and treaties in foreign relations law? This question that has long engaged foreign relations scholars has found new salience in recent years, as the courts have been called repeatedly to determine the meaning of statutes and treaties bearing on the President’s detention and trial powers in combating international terrorism. Among courts noting the confusion on this issue are those now attempting to address whether and to what extent the executive’s views are relevant in interpreting the Authorization for Use of Military Force (AUMF), the statute the President invokes to justify continued detention of terrorist suspects at the U.S. Naval Base at Guantanamo Bay. While the Supreme Court has offered some guidance on the scope of the statute, the AUMF itself is silent on the question of detention. As the courts have struggled to choose between two interpretations of the statute—one put forward by the executive, the other advanced by detainees—courts have been notably equivocal on the potentially dispositive issue of judicial deference: “The Court does not accept the government’s position [on the meaning of the statute] in full, then, even given the deference accorded to the Executive in this realm, because it is ultimately the province of the courts to say ‘what the law is’....”

Historically, most scholars have accepted with little question the notion that the Court will defer to executive views in core matters of foreign relations, particularly where matters of national security are concerned. Yet on descriptive and normative grounds, the events of the past decade have called the prevailing account into question. In treaty interpretation, the Court has invoked a Marbury-based insistence on asserting its own formal interpretive authority. As the Court put it perhaps most dramatically in recent opinions construing the Vienna Convention on Consular Relations: “If treaties are to be given effect as federal law under our legal system, determining their meaning as a matter of federal law ‘is emphatically the province and duty of the judicial department,’ headed by the ‘one supreme Court’ established by the Constitution.” Likewise, in a series of decisions involving national security, the Court has been anything but deferential to the executive’s interpretation of the relevant statute or treaty. In Rasul v. Bush, Hamdi v. Rumsfeld, and Boumediene v. Bush, the Court has swept aside vigorous arguments by the executive that it refrain from engagement on abstention or political question grounds. Moreover, the Court has scarcely noted any doctrinal tradition of interpretive “deference” on the meaning of the laws. While descriptive claims that the Court invariably defers to the President in foreign relations law interpretation have always been subject to challenge, the Court’s recent behavior has made this account increasingly untenable.

In the wake of such decisions, scholars have turned renewed attention to the task of identifying a doctrine of “deference” in foreign relations law. Cass Sunstein and Eric Posner, among others, have expressed the normative concern that the Court, unduly interested in “saying what the law is” in an area of questionable judicial competence, was no longer taking sufficient account of the executive’s superior expertise and political responsiveness in this realm. Others, while not necessarily lamenting the less deferential judicial role, have focused on the importance of finding some constraining approach that would provide interpretive guidance to the courts. If there is no predictable or sensible way of determining how much attention the Court will pay executive views in construing foreign relations law, rule-of-law interests require, at a minimum, the development of a new understanding of the judicial relationship to the executive on questions of law interpretation. Responding to such concerns, Sunstein and Posner thus joined Curtis Bradley and others in suggesting that courts should defer to the executive in cases with “substantial foreign relations implications,” just as they do under Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc. in the standard administrative law context.