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The U.S. Constitution and International Law

Abstract and Keywords

This chapter examines controversies surrounding the U.S. Constitution’s relationship to international law, with particular emphasis on the separation of powers, federalism, the supremacy clause, and individual rights. Before discussing tensions between “original” understandings of international law and the U.S. Constitution, the chapter provides an overview of the founding of the Constitution and its focus on international affairs and foreign relations. It then considers what the Constitution says about treaty law and other international agreements, along with U.S. law’s jurisdiction and supremacy over customary international law. Finally, it explores how international law is interpreted by U.S. law, and how the overlap between international law and constitutional law has increased.

Keywords: international law, separation of powers, federalism, supremacy clause, individual rights, Constitution, international affairs, foreign relations, treaty law, international agreements

*Constitutions face outward as well as inward. They are generally written for both domestic and foreign audiences and to serve both domestic and international purposes. They signal to the world the presence and identity of an independent nation, entitled to be treated as such by other nations, while at the same time constituting an effective working government. Their concerns are in part dignitary and expressive, and in part functional.

Those framing the U.S. Constitution were intensely concerned about the young country’s international standing and capacity to deal effectively with a set of foreign relations challenges.1 International law informed the drafting of much of the text of the Constitution in 1787; international law has, moreover, been an interpretive source, consulted by U.S. courts on constitutional issues over time.

In recent years intense controversy has arisen over the Constitution’s relationship(s) to international law. The controversy is in part about the nature of the Constitution and how it should be interpreted, and in part about expressive feelings of national pride, affiliation, and identity. Disagreements over the nature of international law and its relationship to the U.S. constitutional order are pervasive, turning up in separation-of-powers disputes, understandings of federalism and the meaning of the supremacy clause, and disputes over the meaning of individual rights.

This chapter explores tensions between “original” understandings of international law and the Constitution and significant changes, both in the relative position of the United States and the nature of international law itself, that, I suggest, have resulted in evolution of those understandings. The subject matter of international law has expanded significantly in the last two-hundred-plus years, as has the manner by which it is formed. Over the same period, constitutional law has grown, by amendment and by incremental accumulation of (p. 922) decisions, and the geostrategic position of the United States has changed from a relatively weak new nation to an established, strong, and (to some) hegemonic world power. As both U.S. constitutional law and the scope of international law expand, occasions for conflict are more frequent, and striking shifts in constitutional understandings have emerged over time.

I. Constitutional Founding and Text

International affairs and foreign relations were central concerns for the struggling new country after the Revolutionary War ended. The Articles of Confederation were unworkable in important part because the national government lacked power to enforce treaty obligations and “to frame and implement satisfactory foreign policies.”2 The challenges included inadequate authority to protect American commerce, as well as an inability to enforce provisions of the Treaty with Great Britain providing protection for British property, which “had not been adequately protected by state courts after independence.”3 Britain used such treaty noncompliance as a basis for refusing to remove its troops from forts in Detroit, Oswego, and Niagara.4 Other areas of the country also faced foreign threats: Spain closed off the Mississippi, thereby imperiling commerce, threatening the benefits of the territorial settlement of the Peace Treaty, and increasing the possibility that the United States would disintegrate into multiple competing nations.5

The text that emerged from the Constitutional Convention plainly reflected the Framers’ interests in promoting compliance with international law.6 Each of the three branches of the national government was given authority over matters touching international law. Under Article I, Congress has power “To define and punish piracies and felonies committed on the high seas, and offenses against the law of nations.” This is the Constitution’s only explicit reference to the “law of nations,” the precursor to what is now called customary international law. Congress also has the power to “regulate Commerce with foreign nations,” which may interact with the treaty power discussed below, and “to regulate Commerce … with the Indian Tribes,” a relationship that has been interpreted in light of international law principles.7 Congress’s power to establish a “uniform Rule of Naturalization” may implicate the interests of other nations in the treatment of their nationals. Congress is also given important war-related powers. Congress has the power, for example, to raise armies, and “[T]o declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water,” a provision that has raised questions whether by implication the president does or does not possess overlapping powers.8 (p. 923) Finally, by virtue of the “necessary and proper” clause, Congress has the power to enact legislation to “carr[y] into Execution” powers granted to other branches—a power conventionally understood to permit Congress to legislate to implement treaties, or to effectuate the jurisdiction of the courts.

Article II vests in the president “the executive Power,” a phrase that, some argue, carries with it authority over aspects of foreign relations and national security decisions implicating international law.9 The president’s powers as “Commander in Chief of the Army and Navy” were measured by reference to the international law of war in the Prize Cases;10 President Abraham Lincoln himself in proclaiming the blockade stated that he was acting “pursuant to the laws of the United States and the law of nations.”11 Moreover, the president has “power, by and with the advice and consent of the Senate, to make treaties, provided two thirds of the Senators present concur,”12 thereby establishing an alternative lawmaking procedure that excluded the House of Representatives. Finally, the president is given authority to “nominate, and by and with the advice and consent of the Senate, … appoint ambassadors, other public ministers and consuls”13 and to “receive Ambassadors and other public ministers” from foreign countries,14 which has been construed to include the power to “recognize” foreign governments as legitimate.15

Although “executive agreements,” entered into with foreign nations by the president, acting alone, have come to assume an important role in modern foreign relations, the Constitution’s text does not explicitly address them. It does, however, in Article I, section 10, distinguish between “Treaties,” which states are absolutely forbidden to enter into, and “Agreements” with foreign powers, which states may enter into provided that Congress approves. Some scholars argue by implication that the Constitution contemplates some agreements with foreign states that do not require Senate consent as “treaties.” This argument, based on an assumption of some coherence between the text of Article II and the text of Article I, Section 10, is reinforced by the long practice of executive agreements.16 Similarly, whether the treaty power precludes the use of ordinary legislation (“congressional-executive agreements”) to implement international agreements, has been debated.17

The Articles of Confederation had not provided for standing national courts by which legal obligations could be subject to adjudication and enforcement (apart from an appellate court for prize cases).18 Article III of the Constitution provided a national judiciary and several separate “heads” of jurisdiction relevant to enforcing international obligations. The Article III courts are given jurisdiction over “all Cases, in Law and Equity, arising (p. 924) under … Treaties made, or which shall be made, under” the authority of the United States; “all cases affecting Ambassadors, other public Ministers and Consuls;” and “ all Cases of admiralty and maritime Jurisdiction.” Both treaty law and “admiralty and maritime” laws are international in character. Article III also provided for the judicial power to extend to cases between citizens of the United States and foreign citizens, subjects, or states, and provided specifically that in cases “affecting Ambassadors, ” the Supreme Court has original jurisdiction.

Remedying other perceived defects of the Articles of Confederation, Article IV gave Congress explicit authority both to govern territories of the United States and to admit new states to the Union. In so doing it arguably authorized the acquisition of territory, though this point occasioned much controversy, with some arguing that the United States lacked such power, and others arguing that power to acquire territories was an aspect of the treaty or warmaking powers.19

Under the supremacy clause of Article VI, treaties made under authority of the United States are part of the “supreme Law of the Land,” and must be given effect by state court judges notwithstanding “any Thing in the Constitution or Laws of any State to the Contrary.” Thus, both federal and state courts were enlisted to give effect to treaty obligations, violation of which had occasioned such tension under the Articles.20 Whether the supremacy clause mandates judicial enforcement of customary international law (not the subject of treaties) notwithstanding state law (which came to be the conventional view), has been subject to considerable recent debate.21 But the supremacy clause plainly imposes an affirmative obligation to give effect to the supreme law of the land, including treaties.

There are also a number of constitutional prohibitions, found largely in Article I, Section 10, describing what the states must not do that relate to international law matters. Of particular relevance here are the absolute prohibitions on the states “enter[ing] any Treaty, Alliance, or Confederation,” and against states granting “letters of Marque and Reprisal.” Article I, Section 10 also prohibits states from certain acts, unless Congress consents. Thus: “No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops or Ships of War in time of Peace, enter into any Agreement or Compact with another State or with a foreign Power, or engage in War, unless actually invaded, or on such imminent Danger as will not admit of delay.” By this clause, the Constitution suggests a distinction between a “Treaty, Alliance or Confederation,” which are absolutely prohibited to the states, and an “Agreement or Compact,” to which Congress may consent. States are also prohibited, without congressional consent, from keeping troops or warships in time of peace, or to “engage in War” except under limited and urgent circumstances. The terms “war” and “peace” invoke prevailing concepts of international law. Article I, Section 10 also (p. 925) limits states’ power to regulate commerce through financial impositions, providing: “No State shall, without the Consent of the Congress, lay any imposts or duties on imports or exports,” preserving national government authority with respect to regulations of commerce among the states and with foreign nations.

These provisions provided only a partial and incomplete framework for resolving the many issues about the relationship between the Constitution and international law that would arise. In its early years, members of the Court unself-consciously reached for principles of international law as well as common foreign practice to illuminate constitutional meaning, and with an assumption that what the Constitution required or authorized was consistent with international law, for example, in the treatment of ambassadors, or in the adjudication of admiralty disputes.22 Both constitutional and international law were invoked to support Lincoln’s actions in calling for the blockade of the seceding states.23 The next sections address selected issues concerning the relationships of international law (of different types) to constitutional law, issues that illustrate the kinds of gaps and interpretive issues that time has revealed to exist in the textual framework.24 In so doing, I explore the relationship of original constitutional understandings to contemporary practices, in light of changes in domestic practice and in international law’s nature and content.

II. Treaty Law and Other International Agreements

Of the different forms of international law, the Constitution speaks most clearly on the supremacy of treaties “made, or which shall be made, under the authority of the United States,” language understood to assure the continued force, after adopting the Constitution, of preexisting treaties. As Louis Henkin observed, the meaning of a “treaty” for constitutional purposes was not defined, but definition was assumed based on “what was well known in international law and practice.”25 While the treaty power is a very old, and textual, power, in at least three different areas constitutional understandings have arguably been modified—at times to accommodate, at others to resist, perceived changed circumstances. Thus, even this apparently clear power is not immutable, suggesting the force of events—which may be somewhat indeterminate—on “textualist” or “originalist” modes of interpretation.

(p. 926) 1. Executive Agreements and the Growth of Executive Power

A sole “executive agreement” is one made between the executive branch and a foreign nation that has not been ratified by the Senate or enacted into legislation by the whole Congress. There is ample reason to believe that even as an original matter, the treaty power was not understood to preclude all such agreements.26 But what, if any, limits on executive agreements are implied by the provisions for ratifying treaties? What is the domestic legal force of executive agreements vis-à-vis contrary state law?

President Franklin Delano Roosevelt’s recognition of the Soviet Union gave rise to two important cases concerning executive agreements and their trumping effects on state law property rights. The president’s power to make the “Litvinov agreement” was traced to the power to receive ambassadors and, impliedly, to recognize governments;27 power over “external affairs” was vested “exclusively” in the national government.28 By the agreement with and recognition of the Soviet Union, United States v. Belmont said, the United States had “validate[d], so far as this country is concerned, all acts of the Soviet government here involved …” including confiscations of bank deposits and their assignment to the United States, and New York had no power to treat the confiscation of deposits as illegal.29 Indeed, “the external powers of the United States are to be exercised without regard to state laws or policies. The supremacy of a treaty in this respect has been recognized from the beginning.”30 And this supremacy extended as well to executive agreements:31 “In respect of all international negotiations and compacts, and in respect of our foreign relations generally, state lines disappear. As to such purposes the state of New York does not exist.”32

In United States v. Pink, another dispute arising from the same agreements, the Court, while noting that treaties should be construed so as not to derogate from state authority, insisted that “state law must yield when it is inconsistent with or impairs the policy or provisions of a treaty or of an international compact or agreement.”33 As in Belmont, a strong position of exclusive federal power to preempt state law was asserted: “Power over external affairs is not shared by the States; it is vested in the national government exclusively.”34

In the decades since, executive agreements on subjects less directly related to the president’s power to recognize foreign governments have been upheld and applied to preempt state law, while at the same time there has been increased reliance on congressional-executive agreements.35 Congressional-executive agreements raise relatively small questions of constitutional (p. 927) law, hinging on the difference between the two-thirds of the Senate required for treaty ratification and the voting rules for ordinary legislation in the House and Senate. But sole executive agreements raise larger questions of constitutional law, as they arise without any formal involvement by either house of Congress.

In Dames & Moore v. Regan,36 the president’s power to make an executive agreement with preemptive domestic effect was recognized in the context of an emergency—U.S. citizens being held hostage in the American embassy in Iran. The Court found that a long history of executive claims settlement, acquiesced in by Congress, had established that the president had authority to settle claims disputes with foreign nations. Thus, even though there was no statutory authority for the president to do so, his agreement with Iran that claims pending against Iran in U.S. courts would be suspended was deemed a valid and enforceable law.

While Dames & Moore emphasized the very “narrow” character of its holding,37 American Insurance Ass’n v. Garamendi38 recognized much broader authority, upholding the preemptive force of an executive agreement with Germany concerning compensation of Holocaust survivors. Unlike in Dames & Moore, there was no risk of new harm to U.S. citizens by waiting to submit legislation to Congress. Nor was there a time-sensitive crisis—the claims in question had been unresolved for decades. Moreover, the agreement in question did not clearly state that it was preemptive of state law. The Court nonetheless found that because the agreement required the executive to advise that it was the policy of the United States that any such claims be satisfied out of the fund Germany was establishing, state law claims concerning information about ownership of property covered by the agreement were preempted.

Garamendi has been subject to sharp critique for undermining the protections for state interests provided by the Constitution’s lawmaking processes. Either legislation by majorities of the Senate and the House, or a treaty with agreement of two-thirds of the Senate, would provide more opportunities for the states to advance and protect their interests than exclusively executive lawmaking through negotiated agreements with foreign powers. Whether one should see Garamendi as an appropriate accommodation to the fact of increased executive authority more generally, in the United States and in other constitutional democracies, or as an unfortunate capitulation to executive lawmaking without the protections afforded by treaty or regular lawmaking processes, is debatable.39

(p. 928) 2. Treaty Power Scope and Congress’s Power to Implement Treaties

Can Congress enact legislation to implement a treaty if the legislation were not otherwise authorized by Article I? In Missouri v. Holland40 the Court held yes. This decision had long been thought to settle the scope of Congress’s legislative authority to implement treaties, in the face of Tenth Amendment objections,41 though it has recently come under challenge.

In Holland, Justice Oliver Wendell Holmes Jr. famously concluded that the Tenth Amendment—and the reserved powers of the states—did not limit Congress’s authority to implement valid treaties. Although some of Holmes’s language has been read to suggest that the Constitution imposed no constraints at all, it seems clear that Holmes was distinguishing between the powers of the states “reserved” to them by the theory of enumeration, supported by the Tenth Amendment, and the “prohibitory” portions of the Constitution. These “prohibitory words” might include specific provisions protecting federal interests of the states, such as the prohibition on Congress imposing “export taxes,” as well as provisions of the Bill of Rights, for example, the First Amendment’s ban on any “law … abridging” freedom of speech.42

In Reid v. Covert,43 a plurality took this approach, concluding that “no agreement with a foreign nation can confer power on the Congress, or on any other branch of Government, which is free from the restraints of the Constitution,” including the Fifth and Sixth Amendment rights of civilians to jury trials in criminal cases.44 In oft-quoted reasoning the plurality said

[T]he reason treaties were not limited to those made in “pursuance of the Constitution” [in the supremacy clause] was so that agreements made by the United States under the Articles of Confederation, including the important peace treaties which concluded the Revolutionary War, would remain in effect. It would be manifestly contrary to the objectives of those who created the Constitution … to construe Article VI as permitting the United States to exercise power under an international agreement without observing constitutional prohibitions.45

Henkin treated the plurality opinion as simply confirming that “it is settled that treaties are subject to constitutional limitations.”46 The question remains: Which ones?

The conventional understanding by the late twentieth century was that the treaty power was not limited by the federalism implications of the Tenth Amendment, but that treaties cannot authorize violations of the “prohibitory” provisions of the Constitution, possibly including some limited federalism-based prohibitions but largely those protecting individual rights;47 and relatedly, that Congress could implement treaties even if it would lack power to so legislate absent the treaty.48

(p. 929) Although Missouri v. Holland had for many years been taken as settled law,49 new contests over the scope of the treaty power and of Congress’s implementation powers have arisen, some of which were noted, but not resolved, in Bond v. United States.50 Some scholars have explored the extent to which the subject matter of “treaties” is limited by the Constitution. For Holmes, a treaty addressed interests that “can be protected only by national action in concert with that of another power.”51 Other case law invokes two ideas: first, that of matters of international concern, or matters typically subject to treaties;52 second, that treaties cannot “authorize what the Constitution forbids, or a change in the character of the government or in that of one of the States, or a cession of any portion of the territory of the latter, without its consent.”53 In 1968, Henkin summarized conventional understandings as being that “a treaty would be invalid not only if it were inconsistent with the Bill of Rights or other provisions of the Constitution, but also if it dealt with a matter which was not of “ ‘international concern.’ ”54 Still other possible substantive limits are derived from structural concerns that treaty making not be undertaken for the sole purpose of eliding domestic constitutional constraints.55 Thus far, no treaty or agreement with a foreign power has been found to exceed subject matter limitations on treaties.

Others have argued that although the subject matter of the treaty-making power is largely unencumbered by constitutional constraints, Congress’s authority to implement treaties by statute is limited to the existing confines of its enumerated powers.56 Curtis Bradley’s argument draws from recent federalism decisions in which the exercise of clearly enumerated powers was found constrained by the Tenth Amendment: why should the treaty power be any different, he implicitly asks.57 The logic of Missouri v. Holland, and more generally of the Court’s emphasis on the exclusivity of federal power in foreign relations matters, is that doctrinal rules inspired by the Tenth and Eleventh Amendments—barring “commandeering” of state and local governments, or precluding Congress from authorizing suits against states to enforce certain federal laws—might not apply to treaties and federal statutes designed to implement them. One could imagine treaties that might require the parties to assure that appropriate compensatory relief is available to victims of treaty violations by member states and their subunits: Does the sovereign immunity of the states protect them from obligations agreed to by the United States by treaty? But a number of scholars have argued, or been willing to concede, that “commandeering” and “sovereign immunity” are in the nature of rights of the states, or “prohibitory” constitutional principles and that, unlike subject matter limits implied from the enumeration of powers to the federal government, the states’ constitutional rights cannot be overridden by treaty.58

(p. 930) The point here is the non-immutability of seemingly foundational understandings of the treaty power. In the 1950s human rights treaties were a political anathema and constitutionally questionable; by the 1990s, there was broad consensus on the value of human rights treaties, and on the power of Congress to implement those treaties regardless of whether it had the power to enact similar legislation in the absence of a treaty. But this view was soon to be challenged by revisionist writers, concerned with the impact on U.S. democracy.

Three justices have recently opined (1) that the treaty power is bounded by subject matter limitations to matters of international concern, casting doubt on the validity of human rights treaties that apply generally rather than being limited to the rights of foreigners; and/or (2) that Missouri v Holland was mistaken in holding that the Congress has a power to implement treaties through legislation that, absent the treaty, it could not enact.59 Two of these justices expressed concern that, given the broadening scope of international law in the decades since World War II, “Holland places Congress only one treaty away from acquiring a general police power.”60

Undoing Missouri v Holland could be profoundly disruptive: The idea that a national government could make an internationally valid and binding agreement that it lacked power to enforce, especially against its subnational parts, is one likely to produce mischief. It is a challenge to the idea of the rule of law,61 and inconsistent with the “axiom” that the judicial power should be coextensive with the lawmaking power.62 It seems doubtful that either as an original matter of constitutional purpose or as a practical matter of good constitutional governance a change from this aspect of Missouri v Holland would be salutary.

3. Non-self-executing Treaties, the Changing Force of the Supremacy Clause, and Medellín’s Rejection of a Presumption Favoring Judicial Enforcement

A particularly clear example of a shift from Founding understandings concerns the legal force of treaties. Historians are largely agreed that a critical consideration in drafting the Constitution was to offer a powerful signal, and commitment, that the United States would honor its international obligations, at a time when its perceived failure to do so provoked disrespect and hostile action from foreign governments. The supremacy clause’s inclusion of treaties in the “supreme Law of the Land” clause was a key element in assuring this recognition.63

(p. 931) In its earliest major federalism decisions, the Supreme Court gave self-executing effect to treaty provisions designed to secure British owners of their rights in property.64 As Carlos Vázquez has shown, among the early justices, both James Iredell, the most skeptical of national power on the Marshall Court, and the more Federalist Joseph Story, were in agreement that the effect of the supremacy clause was to require that treaties be treated as law, enforceable by courts, rather than as executory contracts dependent on later action by the legislators.65

To be sure, the Court has long recognized that some treaties contemplate the need for legislation before their obligations could be judicially enforced (including treaties requiring the creation of criminal statutes, or requiring the appropriation of funds).66 But “non-self-executing” treaties were regarded as the exception, not the rule, consistent with the overarching purpose of the supremacy clause. In many early cases, the Court regarded treaties as self-executing in litigation, especially where the treaties conferred rights on or protected individuals.67

Any presumption in favor of treaties being regarded as self-executing was seemingly abandoned by the Court in a series of case dealing with detainee rights under the Vienna Consular Convention (VCC). Article 36 VCC provides that if a foreign national is detained, his consular officials may visit and communicate with him and arrange for his legal representation; it further provides that, on request, the holding government “shall, without delay, inform the consular post of the sending State … and shall inform the person concerned without delay of his rights under this sub-paragraph.”68 In cases involving death-sentenced foreign nationals who did not receive the required consular advice, the Court has consistently refused to provide any form of judicial relief for violations of this seemingly clear mandate, either on direct criminal appeal or on collateral review.

In Sanchez-Llamas v. Oregon,69 while assertedly reserving the question whether the VCC was self-executing, the Court appeared to question whether the provision of article 36 that the government “shall … without delay” inform the person of his rights as created a basis for any judicially inferred remedy: “where a treaty does not provide a particular remedy, either expressly or implicitly, it is not for the federal courts to impose one on the States through lawmaking of their own.”70 The Court relied on the practices of other signatories to imply that there would be no reason for the United States to reach a different conclusion,71 not discussing the supremacy clause’s original purpose to provide assurances of the enforceability of treaties to a greater extent than existed in Europe at the time.72

(p. 932) The Court’s concern to protect states from having to provide remedies to vindicate treaty rights was more apparent in Medellín v. Texas,73 which suggests that any presumption once provided by the supremacy clause in favor of judicial enforcement of treaties was no more. The VCC’s Optional Protocol, which the United States chose to ratify, provides for the jurisdiction of the International Court of Justice (ICJ) with respect to disputes under the Convention. The ICJ concluded that in the case of fifty-one named individuals from Mexico, there had been violations of consular rights and that the United States was obligated to provide some form of review of those convictions to determine whether the violations were so prejudicial as to warrant relief.74 The president issued a memorandum indicating that the United States would fulfill its obligations under the Avena judgment by asking the state courts to reopen proceedings.75 But the Supreme Court interpreted the UN Charter’s provisions establishing the ICJ, as well as the VCC’s Optional Protocol, to establish no self-executing obligation to comply with the judgments of the ICJ: UN Charter article 94 states only that the parties “undertake to comply” with ICJ judgments, and contemplates referral to the Security Council for enforcement. Thus, the Court concluded, the primary enforcement of these rights was intended to be diplomatic. The Court further held that because the treaties were non-self-executing, they implied that the Senate did not intend to allow the president to enforce them through preemptive law.76

Medellín works important shifts in understanding whether treaties are presumptively self-executing, which move the United States closer to a “dualist” than a “monist” constitutional state. Whether it is accurate to say that there is now a presumption that treaties are not self-executing, it seems clear that any presumption that treaties—as the supreme law of the land—are judicially enforceable has been abandoned. The change in the power position of the country from the founding to the present may help account for the Court’s unwillingness to presume in favor of self-execution, and its new insistence that the self-executing character of a treaty must be “reflect[ed] in a determination by the president… and the Senate… that the treaty has domestic effect.”77 Not only the increased geostrategic power of the United States, but also the changing valence of “federalism”-based claims across constitutional law, may contribute to this development.78 But as people of different nationalities increasingly interact, all countries—including the United States—have interests in assuring respect for international law, interests given surprisingly little weight in the VCC opinions,79 raising concerns that the Court may have weakened international law and U.S. capacity to influence its development.80

(p. 933) III. Customary International Law: Jurisdiction, Supremacy, and Interpretation

A recurring question in recent years has concerned the force, and nature, of customary international law (CIL) in the United States. Is CIL part of U.S. law? Is it “supreme” over state law for purposes of the supremacy clause? Is it federal law for purposes of the jurisdiction of the federal courts? Or is it a general body of law, available to supply rules of decision only when controlling federal, or state, law make it relevant? These questions are ones of increased difficulty, especially in light of post-Erie assumptions about the nature of law and of U.S. constitutional federalism. The challenges have been only compounded by the increased overlap between the subject matter of constitutional law and international law.

In the first century of U.S. constitutional history, the law of nations was accepted as both a guide to the interpretation of other sources of domestic law and as a “part of our law” itself. In Murray v. The Schooner Charming Betsy,81 the Supreme Court, through Chief Justice John Marshall, treated the law of nations as a powerful interpretive guide, explaining why U.S. law could not be understood to violate rights of neutrality: “an act of Congress ought never to be construed to violate the law of nations if any other possible construction remains.”82 In the Prize Cases (1863), the legality of President Lincoln’s blockade was measured in part by reference to the customary laws of warfare.83 And in Paquete Habana (1900), in evaluating whether a seized ship should be returned to its owner, the Court consulted international law and emphasized: “International law is part of our law, and must be ascertained and administered by the courts of justice of appropriate jurisdiction as often as questions of right depending upon it are duly presented for their determination.”84

But precisely what it means to be “part of our law” is now contested. In the late eighteenth, nineteenth, and for much of the twentieth century, jurists assumed that some forms of law were defined or discovered by courts in adjudication. These forms of law included the “common law,” the law of “admiralty and maritime” matters, and the “law of nations”—all which are referred to in the original Constitution or first Ten Amendments.85 The view that some forms of law simply exist and are reflected in the decisions of federal and state courts (and courts of other countries) was subject to critique as, in Justice Holmes’s words, a fictive “brooding omnipresence,” ostensibly discoverable by right reason, but in fact the product of governmental choice.86

In the same time period that state common law decisions were being reconceptualized as the positive law of each separate state in Erie Railroad v. Tompkins,87 other subjects were increasingly being categorized as belonging to a distinctively federal sphere. So it was with the law of nations. By the time of the Restatement (3d) Foreign Relations Law (1987), the conventional understanding was that customary international law is a form of (p. 934) federal common law—for purposes of “arising under” jurisdiction in Article III and for purposes of the supremacy clause, giving preemptive force to federal sources of law.88 Within a decade, however, this conventional understanding was challenged by an influential group of revisionist scholars led by Curtis Bradley and Jack Goldsmith, who argued that customary law had been regarded as a form of general, not federal, common law. In the post-Erie world, they contended, customary international law could not be viewed as federal common law,89 given that it was created through the practices and felt obligations of many countries; moreover, the growth of its subject area meant that giving it preemptive force would burden democratic lawmaking processes within the states.

The principal locus of the dispute over the status of customary international law since the 1990s has concerned questions about the Alien Tort Statute of 1789 (ATS), under which, in the 1980s, foreign nationals began suing other foreign nationals for violations of customary international law. Because these disputes were not within the diverse-party heads of jurisdiction, there was no Article III jurisdiction unless the law of nations were itself a form of federal law. Many scholars defend the Restatement (3d) position, that CIL be considered a form of federal law, relying importantly on history.90 Others join the revisionists, arguing that CIL, having previously been understood as part of the “general law,” is not “federal” law for purposes either of the supremacy clause or of the Article III heads of jurisdiction, unless a norm found in CIL is, for reasons grounded in federal law, adopted as a federal common law rule.

A third group of scholars adopt intermediate positions: that CIL is for some, but not for all, purposes a form of federal law (for example, as nonpreemptive under the supremacy clause but jurisdictionally federal for Article III purposes),91 or as a “third” form of law, neither federal nor state but capable of being applied by federal courts that otherwise have jurisdiction.92 Ernest Young, for example, has argued that CIL may be “part of our law,” through operation of choice-of-law rules;93 defending the concept of a “general law” of CIL, he is willing to allow federal common law constraints on state choice-of-law rules. Linking the supremacy clause with structural concerns for federalism, Bradford Clark argues that the only form of federal law with preemptive force is the Constitution or laws “made” under the Constitution, including statutes or treaties—but that international law informs understanding of some constitutional terms, and that some aspects of customary (p. 935) international law should be viewed as incidents of constitutional allocations of powers and thus as federal law unless changed by Congress.94

In Sosa v. Alvarez-Machain,95 the Supreme Court suggested that at least some forms of customary international law could be viewed as federal law for jurisdictional and supremacy clause purposes. It held that the particular violation of which the plaintiff complained was not actionable under the ATS, because the ATS was limited to violations of customary law that were as clear and accepted as was piracy or attacks on ambassadors at the founding period. Although the Court was ambiguous, its reasoning strongly implied that at least some parts of customary international law could be treated as a form of federal law, at least for purposes of Article III arising-under jurisdiction.96

In recent decades there has been tremendous growth in claims about the scope and content of CIL, sometimes influenced by treaties not ratified, or ratified only with reservations, by the United States. For these and other reasons described elsewhere,97 a cautious and selective approach (perhaps more generous than that implied in Sosa, but not a wholehearted embrace of all that may be claimed as CIL) might help advance international law as law and the capacity of the Constitution to preserve decisions for internal democratic politics.

IV. Interpretation More Generally

Some constitutional provisions cannot fulfill their constitutional function without reference to international law.98 Understanding the scope of Congress’s enumerated powers to define “offenses against the law of nations” requires resort to international law, and not just to international law as it existed at the founding; the Court has recognized that such international law understandings may be evolutionary.99 Likewise, determining what is a “treaty,” or an “agreement or compact” with a foreign nation, or an “ambassador,”100 requires some resort to international understandings or else these provisions would fail of their purposes.

International law also helps define other national powers, especially when statutes are silent. As noted earlier, international law has been treated as bearing on the scope of the president’s wartime powers.101 And in Brown v. United States,102 Chief Justice Marshall appeared to construe the effects of a declaration of war under the Constitution to be in (p. 936) accord with the law of nations in not, of itself, authorizing the extinguishment of enemy property. His discussion emphasized the reciprocal nature of the law of nations as bearing on the interpretation of the U.S. Constitution: “[i]n expounding [the U.S.] constitution, a construction ought not lightly to be admitted which would give to a declaration of war an effect in this country it does not possess elsewhere, and which would fetter that exercise of entire discretion respecting enemy property, which may enable the government to apply to the enemy the rule that he applies to us.”103 Contemporary claims for an executive power unconstrained by international law might be understood to assume that the reciprocal principle to which Chief Justice Marshall referred is no longer relevant,104 a questionable proposition.

Separation of powers and federalism issues can be informed by international law in functional and purposive ways. Given the obvious purpose of many constitutional provisions to enable compliance with international law and facilitate the successful conduct of foreign relations, the connection to the current demands of the international system seems obvious. Less obvious, perhaps, is what, if any, connection international law has to the interpretation and implementation of individual rights portions of the Constitution. Some jurists view the rights-protecting provisions of the Constitution as quintessentially domestic in character (both from an expressive point of view and in terms of their legitimate sources of interpretation); others view the individual-rights-protecting amendments as necessarily influenced by “evolving standards”105 that are themselves informed by transnational developments.106

Arguments from the Purpose of Constitutions:

Part of what constitutions do is establish and maintain their country as a state in a world of states, entitled to be treated as such.107 It is entirely consistent with the external purposes of the Constitution to consider international (and foreign) law in interpreting domestic rights provisions. But there is a difference between interpreting constitutions to embody the norms of international law and interpreting constitutions to enable (but not compel) compliance therewith. The latter allows more room for democratic decision-making and contestation.

Arguments from Interpretive Practice: The Eighth Amendment and the Due Process Clauses:

For some constitutional rights provisions there is a long history of resort to transnational legal understandings (not the same as, but related to, international law) to give meaning to constitutional terms. For example, in its first ruling on a federal Eighth Amendment claim, the Supreme Court in 1879 rejected the challenge to a sentence of death by shooting in the Utah Territory in part because “[c]orresponding rules [that] prevail in other countries” supported the practice.108 Since then, it is common for the Court (p. 937) to consider foreign law in resolving claims that particular penalties violate the “Cruel and unusual” punishments clause of the Eighth Amendment.109 Thus, notwithstanding the dissents, the Court’s references in Roper v. Simmons110 to international law (representing the legal views of many nations) and to foreign practice were consistent with long-standing jurisprudence. The Court has at times noted the foreign provenance as a punishment in explaining why its cruelty was inconsistent with the Eighth Amendment,111 and at other times has noted the international community’s condemnation of a particular punishment as evidence of its unconstitutionality, as in the juvenile death penalty case.112

In Trop v. Dulles, a plurality interpreted the Eighth Amendment as embodying “evolving standards of decency,”113 a phrase since adopted by repeated majorities. Those words invite attention to contemporary developments, both in state laws and jury decisions, and in foreign law, in order to understand what is “unusual” as well as to provide a baseline for the evaluation of what is cruel. But the phrase “evolving standards of decency” more broadly captures what one might call a cosmopolitan vision of a Constitution originally designed, as David Golove and Daniel Hulsebosch argue, to secure the respect of the “civilized” countries of Europe for the United States as an international-law-complying nation.

Although the due process clause does not contain specific words inviting attention to contemporary norms, the Court has on occasion manifested a similarly evolutionary view of its meaning, nowhere more clearly than in Hurtado v. California, where the Court linked Magna Carta to the due process clause and wrote:

There is nothing in Magna Charta, rightly construed as a broad charter of public right and law, which ought to exclude the best ideas of all systems and of every age; and as it was the characteristic principle of the common law to draw its inspiration from every fountain of justice, we are not to assume that the sources of its supply have been exhausted. On the contrary, we should expect that the new and various experiences of our own situation and system will mould and shape it into new and not less useful forms.114

On this view, due process—as a “broad charter of public right and law”—may evolve.115 As Justice Anthony Kennedy has said in explaining the Court’s move from upholding to striking down bans on same-sex sexual intimacy, “As the Constitution endures, persons in every generation can invoke its principles in their own search for greater freedom.”116

Arguments from text:

Unlike more modern constitutional instruments, such as Canada’s 1982 Charter of Rights and Freedoms, the U.S. Constitution includes no general “limitations clause” inviting attention to the practices of other “free and democratic” countries in evaluating whether legislation infringing on interests protected by rights can nonetheless be justified.117 Members of the Court have over time associated the values of the due (p. 938) process clause with those of a “free government,”118 providing some basis for learning from what other free governments do insofar as international law bears on this question. Other constitutional text, focused on “reasonableness,” might likewise invite resort to international law as a form of comparative law.119

Arguments from Rule of Law/Coherence:

It has been argued that there is a rule-of-law interest in construing constitutions in pari materia with international (especially human rights) law, in other words, for a Charming Betsy canon in constitutional interpretation.120 On this account, there is an interest in avoiding conflicting obligations, a reason to try to read the two sources of law in harmony. There are further reasons as well. In the 1960s Henkin could write that it was not plausible to think that an act that violates international law for that reason violates the Constitution, as no country in the world would deprive itself of the power to violate international law.121 Today, several countries have incorporated some aspects of international law, typically international human rights law, as of constitutional stature; by contrast, the United States does not treat treaty law, much less CIL, as being of constitutional stature. But given the changing relationship in the world of international law to constitutions, and the recognitional purposes of constitutions, today it might advance national interests in being seen as a respected member of the international community to avoid interpretations of constitutions that would place a country in violation of international law.

Arguments from Constitutionalism:

Considering international law in interpreting domestic constitutions may also help advance constitutionalism. We saw this in the Prize Cases’ resort to international law to measure the scope of the president’s power as commander in chief, as well as in the Court’s interpretation of the authority created by statute in Hamdan v. Rumsfeld.122 The Court in this and other cases assumed that the international law of jus in belli constrained the president’s actions and provides a measure of whether they were constitutionally embraced in the commander-in-chief power.123

Arguments from Epistemic Humility:

To the extent the Constitution stands for broad principles of fairness, Hurtado suggests that no one people have a monopoly on knowledge. Constitutional values are increasingly reflected in aspects of international law. Being open to learning something about shared public law values, about the substance of rights, or about when decisions should be for democratic choice, is consistent with an appropriate degree of epistemic humility.

Although these are some considerable arguments in favor of interpreting the Constitution in ways that harmonize with international law, there are some important objections to doing so. They include the following:

Originalist, Contractiaran Understandings of Constitutional Legitimacy:

“Originalism” as an interpretive theory flowered in reaction to progressive decisions by the Warren Court. Its proponents argue, at core, that unless the Constitution is interpreted in (p. 939) accordance with relatively specific and narrow understandings of its meaning at the time of the Founding, the Constitution loses legitimacy and the courts become overempowered. This is not the place to rehearse the many arguments for and against this position. But it is important to note that U.S. constitutional adjudication often considers original meanings of constitutional provisions, in ways not necessarily typical of other Western democracies, and originalism would cabin uses of transnational sources.

On some versions of originalism, international or foreign law is relevant only if there was an original understanding that they would be, or if the issue in question falls within the domain of “construction” rather than interpretation. As to the first, it is possible to have an originalist understanding that a particular term—such as “treaty,” or “ambassador, “ or “law of nations”—should have a dynamic meaning that will allow it to play its intended role in authorizing and enabling the government to deal with other nations on the range of matters that are the subject of international agreements and concerns. Thus, it is possible that the original meaning of a term was that it should co-evolve with international practice. As to the second, to the extent some originalists embrace the distinction between interpretation and construction, issues that fall into the latter category can be resolved by resort to atextual “external considerations,”124 presumably including international law.

Constitutionalism and Democratic Consent.

There are consent-based theories of originalism, but there are also democracy concerns less related to original decisions and more related to preserving space now for democratic decision-making at the level of both the national and the state governments. As the subject matter of international law expands, there is, many fear, a risk that too ready incorporation of international law as constraining norms will diminish the arena for local and national democratic decision-making. To some extent, these concerns are addressed by last-in-time rules under which both treaties and most elements of customary international law may be overcome by positive law (including later-enacted statutes).125 But if the burden of overcoming international law by new statute is combined with a broad view of what CIL includes, it is not difficult to see that the arena for democratic decision-making may be circumscribed, a reason for caution in the identification of presumptively binding CIL.

Coherence of Law with Culture.

Some argue that because of an “exceptionalist” American legal or popular culture that disdains international and foreign law, their use should be precluded even as interpretive tools.126 There are many difficulties with this argument. For one thing, U.S. history has some strong strains of cosmopolitan internationalism. And culture is not static, but is rather multivoiced and dynamic. Moreover, this view of American exceptionalism is in considerable tension with the originalist views of some of its proponents. But in the end, the concern about maintaining the connection between law and the culture in which it operates is an important one, and supports a cautious approach of engagement rather than a rush to converge with international law.

Balance in a Federal System:

Especially in the rhetoric of U.S. federalism the concept of “balance” implies some structural aspects of the allocation of powers to the national and state governments. Such a balance may be deemed related to the interests in democracy. (p. 940) International obligations are typically assumed by the national government, through deliberative processes in the political branches. To treat international legal norms as ipso facto forms of domestic law, enforceable through judicial interpretation, may detract from state lawmaking and interpretive activities that are an important part of the constitutional federal system.

IV. Conclusion

Decisions about the force and effect of treaties, or of customary law, bear the imprimatur of changing times. International law is of broader scope, and of greater interest to more people in more countries than it was in the eighteenth century. University centers and NGOs are devoted to its elaboration and enforcement; some countries make their reputation as advancing particular lines of international law.127 The overlap between international law and constitutional law has increased; the nature of the interrelationships between international and constitutional law has become thicker. Although the United States is a far more powerful nation than it was in 1789, its position is dynamic. It has interests now, as it did then, in assuring reciprocal respect for basic international norms, which it was in part the purpose of the Constitution to protect. But for many U.S. jurists, considering international law in constitutional interpretation is one thing; giving it dispositive effect across the wide range of issues on which it arguably bears would be in tension with the democracy-preserving purposes of the U.S. Constitution.


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                                                      (*) With thanks to Carlos Vázquez, and the editors of this volume for helpful comments, and to Trisha Jhunjhnuwala for research assistance.

                                                      (1) Golove, D and Hulsebosch, D, ‘A Civilized Nation: The Early American Constitution, the Law of Nations, and the Pursuit of International Recognition’ (2010) 85 New York University Law Review 932; Jackson, V, Constitutional Engagement in a Transnational Era (2010) 6–8, 255–285.

                                                      (3) Kent, J A, ‘A Textual and Historical Case against a Global Constitution’ (2007) 95 Georgetown Law Journal 463, 506.

                                                      (4) Rakove, n 2 above, 27.

                                                      (5) ibid; cf Amar, A, ‘Some New World Lessons for the Old World’ (1991) 58 University of Chicago Law Review 483, 487.

                                                      (6) See Golove and Hulsebosch, n 1 above, 940, 946 (describing how structural constitutional elements, including an independent judiciary, were intended to uphold international obligations).

                                                      (7) See, e.g., Cleveland, S, ‘Powers Inherent in Sovereignty: Indians, Aliens, Territories and the Nineteenth Century Origins of Plenary Powers over Foreign Affairs’ (2002) 81 Texas Law Review 1, 5–14, 25–50, 253–256.

                                                      (8) cf Brown v. United States, 12 U.S. 110, 127–128 (1814).

                                                      (9) See, e.g. Prakash, S and Ramsey, M, ‘The Executive Power over Foreign Affairs’ (2001) 111 Yale Law Journal 231.

                                                      (10) 67 U.S. 635 (1863).

                                                      (11) Presidential Proclamation 81, April 19, 1861, quoted in Bradley, C and Goldsmith, J, Foreign Relations Law: Cases and Materials (5 edn, 2014) 622; see also Witt, J, Lincoln’s Code (2012) 142–163 (describing deliberate choice to invoke “blockade” under international law rather than domestic law “port closure”).

                                                      (12) U.S. Const., article II, section 2.

                                                      (13) ibid.

                                                      (14) U.S. Const., article II, section 3.

                                                      (15) See United States v. Belmont, 301 U.S. 324, 330 (1937).

                                                      (16) cf Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 610–611 (1952) (Frankfurter, J., concurring).

                                                      (17) See n 35 below.

                                                      (18) See Articles of Confederation article VII (1777); Bourguignon, H, The First Federal Court: The Federal Appellate Prize Court of the American Revolution 1775-1787 (1977).

                                                      (19) For nineteenth-century disagreement over whether this clause provided authority for Congress to acquire new properties, or merely authorized governance of existing ones, see Cleveland, n 7 above, 163–181. See also American Insurance Company v. Canter, 26 U.S. 511, 542 (1828) (asserting that the grant of war and treaty powers authorized the acquisition of territory"either by conquest or by treaty").

                                                      (20) The grant of jurisdiction over admiralty was an important head of jurisdiction involving disputes with foreign nationals and affecting foreign nations; disputes in admiralty and on maritime law were decided under what was regarded as a general common law. See Fletcher, W, ‘The General Common Law and Section 34 of the First Judiciary Act of 1789: The Example of Marine Insurance’ (1984) 97 Harvard Law Review 1513.

                                                      (21) For an introduction to the debate, see Bradley and Goldsmith, n 11 above, 406–407.

                                                      (22) See Golove and Hulsebosch, n 1 above, 1006.

                                                      (23) See The Prize Cases, n 10 above, 666–670.

                                                      (24) On the relationship of international law to the Constitution over time, see Cleveland, S, ‘Our International Constitution’ (2006) 31 Yale Journal of International Law 1; Stewart, J, ‘The Status of the Law of Nations in Early American Law’ (1989) 42 Vanderbilt Law Review 819, 828–837.

                                                      (25) Henkin, L, ‘The Constitution, Treaties and International Human Rights’ (1968) 116 University of Pennsylvania Law Review 1012, 1015.

                                                      (26) See Dames & Moore v. Regan, 453 U.S. 654, 679 n.8 (1981}; Bradley and Goldsmith, n 11 above, 375–376; Henkin, L, ‘Treaties in a Constitutional Democracy’ (1989) 10 Michigan Journal of International Law 406, 418.

                                                      (27) For strong expression of this, see United States v. Pink, 315 U.S. 203, 241 (1942) (Frankfurter, J., concurring).

                                                      (28) United States v. Belmont, 301 U.S. 324, 330 (1937).

                                                      (29) ibid 330.

                                                      (30) ibid 330–331 (emphasis added).

                                                      (31) ibid 330.

                                                      (32) ibid.

                                                      (33) Pink, n 27 above, 230–231 (internal citations omitted).

                                                      (34) ibid 233. For an argument seeing these cases as part of a broader shift toward an expansive view of federal power and presidential powers, see White, G E, ‘The Transformation of the Constitutional Regime of Foreign Affairs’ (1999) 85 Virginia Law Review 1, 108–134.

                                                      (35) In the 1990s, NAFTA became the most controversial example of this innovation, under which international agreements are adopted not through a two-thirds vote of the Senate, but through the ordinary lawmaking process. Henkin treated the constitutionality of such congressional executive agreements as settled, Henkin, n 25 above, 422; Henkin, L, Foreign Affairs and the Constitution (2 edn, 1972) 175. Constitutional scholars have since disagreed about this proposition. Compare Ackerman, B and Golove, D, ‘Is NAFTA Constitutional?’ (1995) 108 Harvard Law Review 799 with Tribe, L, ‘Taking Text and Structure Seriously: Reflections on Free-Form Method in Constitutional Interpretation’ (1995) 108 Harvard Law Review 1221. Constitutional challenges to NAFTA’s adoption have been dismissed. See Made in USAFoundation v. United States, 242 F. 3d 1300 (11th Cir. 2001) (nonjusticiable). Whether there are subjects, such as defense treaties, that require two-thirds ratification in the Senate, is a question that remains unresolved.

                                                      (36) 453 U.S. 654 (1981).

                                                      (37) Dames & Moore, n 26 above, 688.

                                                      (38) 539 U.S. 396 (2003).

                                                      (39) See Henkin, n 35 above, 179 (arguing that too expansive a use of executive agreements would “wholly remove the ‘check’ of Senate consent” for treaties). Compare Garamendi with Medellín v. Texas, 552 U.S. 491 (2008) (holding that the president lacked authority to compel state courts to reopen a claim pursuant to the opinion of an international tribunal). The president’s action in Medellín was intended to implement U.S. obligations under multiple ratified treaties, but the Court, having found no self-executing obligations under the treaties, viewed the president’s action as inconsistent with Congress’s intent. Medellín, at 527 (“[T]he non-self-executing character of the relevant treaties … implicitly prohibits” the president from unilaterally seeking to enforce the treaty obligations.). cf Youngstown, n 16 above (rejecting the president’s claim of inherent or commander-in-chief power to nationalize steel industry to promote Korean War supply effort).

                                                      (40) 252 U.S. 416 (1920).

                                                      (41) See, e.g., Henkin, n 25 above, 1018; Damrosch, L, ‘Treaties and International Regulation’ (2004) 98 American Society of International Law Proceedings 349.

                                                      (42) 252 U.S. at 433; see U.S. Const. article I, section 9; ibid amend. I; Damrosch, n 41 above, 349.

                                                      (43) 354 U.S. 1 (1957).

                                                      (44) ibid 16.

                                                      (45) ibid.

                                                      (46) Henkin, n 25 above, 1015.

                                                      (47) See Henkin, n 35 above, 137–140, 147–148, 252–254; Damrosch, n 41 above.

                                                      (48) See Vázquez, C, ‘Missouri v. Holland’s Second Holding’ (2008) 73 Missouri Law Review 939.

                                                      (49) See, e.g., Henkin, n 35 above, 144; United States v. Lara, 541 U.S. 193, 201 (2004).

                                                      (50) 134 S. Ct. 2077 (2014).

                                                      (51) Holland, n 40 above, 435.

                                                      (52) See, e.g., Asakura v Seattle, 265 U.S. 332, 341 (1924); Holden v. Joy, 84 U.S. (17 Wall.) 211, 243 (1872).

                                                      (53) DeGeofroy v. Riggs, 133 U.S. 258, 267 (1890).

                                                      (54) Henkin, n 25 above, 1024.

                                                      (55) See ibid.

                                                      (56) See, e.g., Bradley, C, ‘The Treaty Power and American Federalism’ Part I (1998) 97 Michigan Law Review 390, 429; Rosencrantz, N, ‘Executing the Treaty Power’ (2005) 118 Harvard Law Review 1867. For a response to Bradley, see Golove, D, ‘Treaty-Making and the Nation: The Historical Foundation of the Nationalist Conception of the Treaty Power’ (2000) 98 Michigan Law Review 1075.

                                                      (57) See Bradley, n 56 above, 409.

                                                      (58) See Golove, n 56 above, 1087; Vázquez, n 48 above, 942.

                                                      (59) Bond, n 50 above, 2094 (Scalia, J., concurring in the judgment); ibid 2103 (Thomas, J., concurring in the judgment); ibid 2111 (Alito, J., concurring in the judgment).

                                                      (60) ibid 2101 (Scalia J., concurring in the judgment).

                                                      (61) While federalism “reservations” might put foreign powers on notice, their excessive use may also diminish the force of the treaty power.

                                                      (62) Federalist 80 (Hamilton). Although in Canada certain treaties can only be implemented by the provinces, Labour Conventions Case, [1937] UKPC 6, this doctrine has been much criticized; moreover, obtaining subnational level agreement to implement treaties before they are ratified from only ten provinces is more manageable than doing so for fifty states.

                                                      (63) Vázquez, C, ‘Treaties as Law of the Land: The Supremacy Clause and Judicial Enforcement of Treaties’ (2008) 122 Harvard Law Review 599; Golove and Hulsebosch, n 1 above, 995.

                                                      (64) See Ware v. Hylton, 3 U.S. 199 (1796); Fairfax’s Devisee v. Hunter’s Lessee, 11 U.S. 603 (1813); Martin v Hunter’s Lessee, 14 U.S. 304 (1816).

                                                      (65) Vázquez, n 63 above, 620–621.

                                                      (66) See Foster v. Nielsen, 27 U.S. 253 (1827); Bradley and Goldsmith, n 11 above, 279.

                                                      (67) See, e.g., Vázquez, C, ‘The Four Doctrines of Self-Executing Treaties’ (1995) 89 American Journal of International Law 695, 716 n.99.

                                                      (68) Vienna Convention on Consular Relations art. 36, done 24 April 1963, 596 U.N.T.S. 261. (emphasis added)

                                                      (69) 548 U.S. 331 (2006). See also Breard v. Greene, 523 U.S. 371 (1998).

                                                      (70) Sanchez-Llamas, n 69 above, 347; see ibid 337 (assuming without deciding that the VCC may create judicially enforceable rights).

                                                      (71) ibid 344. The Court also held that ordinary procedural default rules would bar consideration of VCC claims not raised at trial. ibid 334–335.

                                                      (72) See Hulsebosch and Golove, n 1 above, 990, 995; Vázquez, n 63, above, 614–616. For a more complex view of prior British practice, see Flaherty, M, ‘History Right? Historical Scholarship, Original Understandings and Treaties as “Supreme Law of the Land” ’ (1999) 99 Columbia Law Review 2095.

                                                      (73) 552 U.S. 491 (2008).

                                                      (74) Case concerning Avena and Other Mexican Nationals (Mexico v. United States of America) 2004 I.C.J. 12 (Judgment of March 31, 2004).

                                                      (75) Medellín, n 39 above, 497.

                                                      (76) ibid 524–528.

                                                      (77) ibid 521; see ibid 519.

                                                      (78) cf Henkin, n 35 above, 5.

                                                      (79) While Sanchez-llamas, 538 U.S. at 353–356, nominally gave the ICJ judgment “respectful consideration,” the Court appeared to give more weight to the practices of other nations than to the ICJ’s reasoning. See ibid 344.

                                                      (80) cf. e.g., Medellín, n 39 above, 556–560, 566–567 (Breyer, J., dissenting).

                                                      (81) 6 U.S. 64 (1804).

                                                      (82) ibid 118.

                                                      (83) Prize Cases, n 10 above.

                                                      (84) 175 U.S. 677, 700 (1900).

                                                      (85) See U.S. Const., article I, section 8; U.S. Const., article III, section 2; U.S. Const., amend. VII.

                                                      (86) Southern Pacific Co. v. Jensen, 244 U.S. 205, 222 (1917) (Holmes, J., dissenting).

                                                      (87) 304 U.S 64 (1938).

                                                      (88) See Bradley, C and Goldsmith, J, ‘Customary International Law as Federal Common Law: A Critique of the Modern Position’ (1997) 110 Harvard Law Review 815, 816 (1997); Restatement (3d), Foreign Relations Law section 111(1).

                                                      (89) See, e.g., Bradley and Goldsmith, n 88 above, 852–856; cf Trimble, P, ‘A Revisionist View of Customary International Law’ (1986) 33 University of California-Los Angeles Law Review 665.

                                                      (90) See, e.g., Koh, H, ‘Is International Law Really State Law?’ (1998) 111 Harvard Law Review 1824; Stephens, B, ‘The Law of Our Land: Customary International Law as Federal Law after Erie’ (1997) 66 Fordham Law Review 393, 397; Vázquez, C, ‘Customary International Law as U.S. Law’ (2011) 86 Notre Dame Law Review 1495.

                                                      (91) See, e.g., Ramsey, M, ‘International Law as Non-preemptive Federal Law’ (2002) 42 Virginia Journal of International Law 555.

                                                      (92) See, e.g., Aleinikoff, T A, ‘International Law, Sovereignty and American Constitutionalism’ (2004) 98 American Journal of International Law 91; see also Weisburd, A, ‘State Courts, Federal Courts, and International Cases’ (1995) 20 Yale Journal of International Law 1, 2–3.

                                                      (93) Young, E, ‘Sorting out the Debate over Customary International Law’ (2002) 42 Virginia Journal of International Law 365, 470.

                                                      (94) Clark, B, ‘The Procedural Safeguards of Federalism’ (2008) 83 Notre Dame Law Review 1681, 1683–1690 and ‘Separation of Powers as a Safeguard of Federalism,’ (2001) 79 Texas Law Review 1321; see Bellia, A and Clark, B, ‘The Law of Nations as Constitutional Law’ (2012) 98 Virginia Law Review 729.

                                                      (95) 542 U.S. 692 (2004).

                                                      (96) See Fletcher, W, ‘International Human Rights in American Courts’ (2007) 93 Virginia Law Review 653, 670–71.

                                                      (97) Jackson, n 1 above, 117–130.

                                                      (98) See Bellia and Clark, n 94 above, 745–799; Cleveland, n 24 above, 19–27.

                                                      (99) See United States v. Arjona, 120 U.S. 479, 485–486 (1887). Debate has emerged on the extent to which Congress is bound by international law in defining offenses triable by military commission. See Hamdan v. United States, 696 F. 3d 1238, 1246 and n.6 (D.C. Cir. 2012).

                                                      (100) See, e.g., 7 U.S. Op. Atty. Gen. 186 (U.S.A.G.), 1855 WL 2298, *196–197 (May 25, 1855).

                                                      (101) See Prize Cases, n 10 above, 641; Hamdan v. Rumsfeld, 548 U.S. 557, 590–95, 613–33 (2006).

                                                      (102) 12 U.S. 110 (1814).

                                                      (103) ibid 125.

                                                      (104) Compare Posner, E and Vermeule, A, The Executive Unbound: After the Madisonian Republic (2011) with Galbraith, J, ‘International Law and the Domestic Separation of Powers’ (2013) 99 Virginia Law Review 987.

                                                      (105) On “evolving standards of decency” in Eighth Amendment law, see Trop v. Dulles, 356 U.S. 86, 101 (1958) (plurality opinion).

                                                      (106) International law and foreign public law may both be relevant in informing an evaluation of how to understand the individual rights guarantees of the U.S. Constitution. But on some theories, international law has special standing. See Jackson, n 1 above, 49–50, 168–177.

                                                      (107) See generally ibid 6–8, 256–262; with respect to the U.S. Constitution, see Golove and Hulsebosch, n 1 above.

                                                      (108) Wilkerson v. Utah, 99 U.S. 130, 134 (1879). cf Cummings v. Missouri, 71 U.S. 277, 318, 320–321 (1867).

                                                      (109) See Jackson, V, ‘Constitutional Comparisons: Convergence, Resistance, Engagement’ (2005) 119 Harvard Law Review 109, n.4.

                                                      (110) 543 U.S. 551, 567, 576 (2005).

                                                      (111) Weems v. United States, 217 U.S. 349, 363–369 (1910).

                                                      (112) Roper, n 110 above, 578.

                                                      (113) Trop, n 105 above, 101.

                                                      (114) 110 U.S. 516, 531 (1884).

                                                      (115) But see Michael H. v. Gerald D., 491 U.S. 110, 127 n.6 (1989) (Scalia, J.).

                                                      (116) Lawrence v. Texas, 539 U.S. 558, 579 (2003), overruling Bowers v. Hardwick, 478 U.S. 186 (1986); see also Jacobson v. Massachusetts, 197 U.S. 11, 31–33 and n.1, 35 (1905); Muller v. Oregon, 208 U.S. 412, 419 n.1 (1908).

                                                      (117) cf U.S. Const., amend. II (referring to what is “necessary to the security of a free state”); but cf District of Columbia v. Heller, 554 U.S. 570, 597 (2008).

                                                      (118) See Powell v. Alabama, 287 U.S 45, 64 (1932).

                                                      (119) cf Calabresi, S and Zimdahl, S, ‘The Supreme Court and Foreign Sources of Law: Two Hundred Years of Practice and the Juvenile Death Penalty Decision’ (2005) 47 William and Mary Law Review 743, 789.

                                                      (120) See Jackson, n 1 above, 54–55, 44 (describing Yuval Shany’s and Michael Kirby’s arguments, respectively).

                                                      (121) See Henkin, n 25 above, 1015.

                                                      (122) 548 U.S. 557, 590–595, 613–633 (2006).

                                                      (123) See Galbraith, n 104, 1047.

                                                      (124) Whittington, K, ‘Constructing a New American Constitution’ (2010) 27 Constutional Commentary 119, 122.

                                                      (125) On the last-in-time rule, see Breard v. Greene, 523 U.S. 371, 376 (1998).

                                                      (126) See, e.g., Calabresi, S, ‘A Shining City on a Hill” ’ (2006) 86 Boston University Law Review 1335.

                                                      (127) See United States v. Burns, [2001] 1 SCR 283, 287 (Can.) (describing death penalty abolition as “a major Canadian initiative” internationally).