Full opinion text
ORDER On Petition for Rehearing En Banc Appellant’s petition for rehearing en banc and the response thereto were circulated to the full court, and a vote was requested. Thereafter, a majority of the judges eligible to participate did not vote in favor of the petition. Upon consideration of the foregoing and the -brief of amici curiae, it is ORDERED that the petition be denied. * A statement by Chief Judge Sentelle and Circuit Judges Ginsburg, Henderson, Rogers, Tatel, Garland, and Griffith, concurring in the denial of rehearing en banc, is attached. * A statement by Circuit Judge Brown, concurring in the denial of rehearing en banc, is attached. * A statement by Circuit Judge Kava-naugh, concurring in the denial of rehearing en banc, is attached. * A statement by Senior Circuit Judge Williams is attached.
SENTELLE, Chief Judge, and GINSBURG, HENDERSON, ROGERS, TATEL, GARLAND, and GRIFFITH, Circuit Judges, concurring in the denial of rehearing en banc: We decline to en banc this case to determine the role of international law-of-war principles in interpreting the AUMF because, as the various opinions issued in the case indicate, the panel’s discussion of that question is not necessary to the disposition of the merits. See Al-Bihani v. Obama, 590 F.3d 866, 871, 873-74 (D.C.Cir.2010) (panel opinion); id. at 883-85 (Williams, J., concurring in the judgment); Al-Bihani v. Obama, No. 09-5051, slip op. at 1 (D.C.Cir. Aug. 31, 2010) (Kavanaugh, J., concurring in the denial of rehearing en banc); see also Gov’t’s Resp. to Pet. for Reh’g and Reh’g En Banc at 1-2 (stating that the dispute over the role of the law of war does not “change[ ] the outcome”).
BROWN, Circuit Judge, concurring in the denial of rehearing en banc: Denial is the fate of most requests for en banc review, and almost all requests meet that fate quietly without comment from the court. I would prefer to follow the usual pattern here. But this, it seems, is no usual case. Neither the government’s response to the request for rehearing nor the opinions accompanying the denial can be described as “usual.” Al-Bihani’s petition requests the court take the radical step of incorporating all of international law as judicially enforceable constraints on the President’s war powers. The government responds ambivalently, adopting the questionable strategy of conceding Al-Bihani’s point, but nonetheless urging denial of rehearing. Seven members of this court now vote to deny the petition, but append a cryptic statement that exhibits no apparent function other than to mystify. One judge offers a scholarly exegesis on the unen-forceability of international law norms as limits on the President’s war-making authority under the AUMF. And last, another judge contributes a separate opinion that conceives of a brave new role for judges in wartime: that of supervisors of the battlefield. These are unusual developments, indeed, and their cumulative effect is to muddy the clear holding of Alr-Bihani that international law as a whole does not limit the AUMF’s grant of war powers. Although we have avoided en banc review, we have done so through the costly expedient of making a rather common-place judicial proposition impenetrably obscure. Clarity in law is a virtue. In the context of war, that virtue becomes a life-and-death necessity. But there appears to be a countervailing motivation behind the court’s resistance to Alr-Bihani’s holding: an intuition about the domestic role of international law, one that moves below the surface of the briefs and opinions of this en banc petition process. Hoping to avoid a resolution that leaves all parties in doubt about international law’s relation to the AUMF, I write separately to pull the veil back on that intuition and provide as much clarity as possible. The Al-Bihani opinion held as “mistaken” the “premise that the war powers granted by” the AUMF and other statutes “are limited by the international laws of war.” Al-Bihani v. Obama, 590 F.3d 866, 871 (D.C.Cir.2010). This holding disposed of Al-Bihani’s international law-based claims and instead hinged the resolution of his case on “the text of relevant statutes and controlling domestic caselaw.” Id. at 871-72. Although Al-Bihani’s rehearing petition challenges the panel opinion on numerous points, it is his challenge to this holding that has caused consternation. Seven judges have embraced a peculiar concurrence that strives to make clear that the holding was not necessary to the disposition of the case, providing four citations to that effect. But the concurrence leaves unclear the reason why this uncontroversial point is relevant. We grant rehearing when a panel opinion creates a conflict with Supreme Court or circuit precedent, or when a case presents a question we deem exceptionally important. See Fed. R.App. P. 35(a). Neither of these criteria is affected when an opinion’s disposition is supported by two independently sufficient alternative holdings. Perhaps the seven-member concurrence is implying that the holding at issue is dictum — a position for which Judge Williams argued explicitly in his separate opinion at the panel stage, see Al-Bihani, 590 F.3d at 885 (Williams, J., concurring). Under this view, the holding would therefore be incapable of either creating a conflict with prior law or presenting an important question. But this notion would be incorrect. It is a longstanding principle that alternative holdings each possess precedential effect. See United States v. Title Ins. & Trust Co., 265 U.S. 472, 486, 44 S.Ct. 621, 68 L.Ed. 1110 (1924) (“[W]here there are two grounds, upon either of which an appellate court may rest its decision, and it adopts both, the ruling on neither is obiter [dictum], but each is the judgment of the court, and of equal validity with the other.”); see also Woods v. Interstate Realty Co., 337 U.S. 535, 537, 69 S.Ct. 1235, 93 L.Ed. 1524 (1949); Commonwealth of Mass. v. United States, 333 U.S. 611, 623, 68 S.Ct. 747, 92 L.Ed. 968 (1948). Therefore, if the majority of this court believes the holding at issue would otherwise satisfy one or both of the en banc rehearing criteria, a grant of rehearing cannot be avoided by labeling the holding as unnecessary. Nor will future litigants be able to avoid the holding’s binding authority by wielding the same label. Another possible motivation for the concurrence may be a desire to accommodate both the government’s eager concession that international law does in fact limit the AUMF and the government’s argument that its opinion on the matter is entitled to “substantial deference.” Resp. to Petition for Rehearing, at 6-8 & n. 3. But such a motivation would be illegitimate. Contrary to the government’s claim, its preferred statutory interpretation warrants no deference from this court. A “pure question of statutory construction [is] for the courts to decide,” INS v. Cardoza-Fonseca, 480 U.S. 421, 446, 107 S.Ct. 1207, 94 L.Ed.2d 434 (1987), and doing so — even when a statute concerns foreign affairs — is “well within the province of the Judiciary,” Repub. of Austria v. Altmann, 541 U.S. 677, 701, 124 S.Ct. 2240, 159 L.Ed.2d 1 (2004). Of course, courts are highly deferential when reviewing challenges to executive actions taken pursuant to a grant of wide discretion “to affect a situation in a foreign territory.” United States v. Curtiss-Wright Export Corp., 299 U.S. 304, 321, 57 S.Ct. 216, 81 L.Ed. 255 (1936). We will refrain from requiring “narrowly definite standards by which the President is to be governed” and will not lightly endeavor to “limit[] or embarrass[] such powers.” Id. at 322, 57 S.Ct. 216. However, even when courts consider the Executive’s historic practice to inform the interpretation of a statute, they are not imbuing the President with judicial power. I sense, then, something more significant than a narrow concern over dictum or deference at work in the seven-member concurrence. There is in the scholarly community an intuition that domestic statutes do not stand on their own authority, but rather rest against the backdrop of international norms. This intuition has taken many argumentative forms, some more emphatic than others. For instance, there are those scholars who believe domestic statutes are merely suggestive wordings to which courts can and should append international legal norms, regardless of congressional intent. Others are more shy, imparting to Congress a general intent to legislate in conformity with international law and therefore reasoning that all statutes, unless containing a clear statement otherwise, should be read by courts to incorporate international legal norms. However this intuition is phrased, perhaps the majority of judges on this court are apprehensive about unambiguously rejecting it. So, even though the panel decision foreclosed the idea, the short concurrence may represent a wish to leave open a possibility — however slight — that domestic statutes are in fact subordinate to an overarching international legal order. If that is their wish, it is a curious one. The idea that international norms hang over domestic law as a corrective force to be implemented by courts is not only alien to our caselaw, but an aggrandizement of the judicial role beyond the Constitution’s conception of the separation of powers. See United States v. Yunis, 924 F.2d 1086, 1091 (D.C.Cir.1991) (“[T]he role of judges ... is to enforce the Constitution, laws, and treaties of the United States, not to conform the law of the land to norms of customary international law.”). That aggrandizement is clear in the more extreme scholarly opinions calling for courts to ignore congressional intent in favor of international norms. And it is only slightly better disguised in the superficially restrained claims that Congress intends to conform its actions with global ideals, and that a clear statement is required if courts are to be prevented from reading international law into statutory text. Traditional clear statement rules are justified on the basis of preserving statutes against possible nullification by a constitutional value, keeping both Congress and the judiciary within their constitutional capacities. However, a demand that Congress clearly enunciate the inapplicability of international norms is not premised on any constitutional value; nothing in the Constitution compels the domestic incorporation of international law. Instead, what such a demand protects is a policy preference, imputing to Congress a general posture toward international restrictions and erecting the highest interpretive hurdle to the legitimate prerogative of Congress to legislate apart from them. This is a restrained search for legislative “intent” only in the most Orwellian sense — one that grants judges license to usurp the legislative role and dictate to Congress what it is supposed to think. Surprisingly, proponents of this idea actually claim it guards the separation of powers. See Wuerth, supra, at 349-50. But if that is the case, then the cure is truly worse than the disease. I see much of this scholarly idea in Judge Williams’ separate opinion. While purporting to share Judge Kavanaugh’s concern about using “gauzy notions of international law to rein in the executive’s conduct of military operations,” infra, at 56 (opinion of Williams, J.), Judge Williams offers a hazy but ominous hermeneutics. Its animating premise is that Boumediene v. Bush, 553 U.S. 723, 128 S.Ct. 2229, 171 L.Ed.2d 41 (2008), used the Suspension Clause to create an opening through which the Judiciary now — as a constitutional matter — “monitor[s]” and “supervise^] the battlefield conduct of the U.S. military.” Infra, at 12-13 (opinion of Williams, J.). In executing this supervisory role, the Judiciary should suxrvey the spectrum of “international discourse,” picking and choosing those propositions that exhibit — by the Judiciary’s lights — “serious reasoning,” “consistent ] and evenhanded[] application],” and “practicality]” to the point where they are suitable to control the President’s conduct of war. Id. at 10, 12-13. Judge Williams states these propositions matter-of-factly, even blithely, as routine matters of statutory interpretation. But that nonchalance is only a mask for what is, at its core, a radical and sweeping claim, one at odds with our Constitution and caselaw. The Constitution entrusts the President — not the Judiciary — with the conduct of war. “The Framers ... did not make the judiciary the overseer of our government,” Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 594, 72 S.Ct. 863, 96 L.Ed. 1153 (1952) (Frankfurter, J., concurring), so Boumediene cannot be read — as Judge Williams suggests — to override that basic notion and hand courts authority to deem international norms as binding commands on the Commander-in-Chief. Such a reading would be in tension with the Supreme Coxxrt’s recognition that courts are “hardly ... competent” in the realm of foreign affairs, Banco Nacional de Cuba v. Sabbatino, 376 U.S. 398, 410, 84 S.Ct. 923, 11 L.Ed.2d 804 (1964), and with the constitutional principle that prohibits even Congress, let alone the Judiciary, from “interfering] with the [Executive’s] command of forces and the conduct of campaigns,” Ex Parte Milligan, 71 U.S. (4 Wall.) 2, 139, 18 L.Ed. 281 (1866) (Chase, C.J., concurring). Further, Judge Williams’ proposed role for the Judiciary goes far beyond the role the Supreme Court envisioned in Hamdi v. Rumsfeld and Boumediene. The Ham-di plurality forecast a restrained process that “meddles little, if at all, in the strategy or conduct of war, inquiring only into the appropriateness of continuing to detain an individual claimed to have taken up arms against the United States.” 542 U.S. 507, 535, 124 S.Ct. 2633, 159 L.Ed.2d 578 (2004). It seems farfetched that “inquiring only into the appropriateness” of detention should be freighted with the awesome power of deciding which international constraints to enforce against the President. In a similar vein, the Court in Boumediene was circumspect about crafting any substantive rules to control the President’s war powers, repeating that it was not addressing the “content of the law that governs petitioners’ detention,” leaving it to the political branches first to engage in a “debate about how best to preserve Constitutional values while protecting the Nation from terrorism.” 128 S.Ct. at 2277. Boumediene’s holding concerned the jxirisdietion of U.S. coxxrts over Guantanamo habeas petitions, and it strains the jurisdictional nature of that holding to draw from it a substantive judicial power to spin international discourse into binding domestic law. It is no wonder then that Judge Williams does not offer any language from Boumediene to support his theory of an expanded judicial role in military affairs. This sprint into judicial immodesty cannot be redeemed by Judge Williams’ argument that international law parallels traditional tools of statutory interpretation, and that by turning to it for substantive meaning eoxirts are only divining the intent of Congress. I am unaware of any federal judicial opinion — and Judge Williams cites none — that has ever before characterized international discourse as a traditional tool of statutory interpretation on par with legislative history, usage in other domestic statutes and cases, or dictionary definitions. The varied process by which international law is made — through treaty, tribunal decision, and the constant churn of state practice and opinio juris — shares few, if any, of the qualities that give the traditional sources of interpretation their authority. Courts turn to legislative history because it comes from the mouths of legislators and therefore arguably sheds light on their intentions and understandings. Courts examine the usage of terms in other statutes and judicial decisions because our law is a closed and coherent system that strives for internal consistency. And courts consult dictionaries for the same reason most people do: our law, like the rest of our society, is dependent on language’s technical meaning among American English speakers. On none of these grounds can the use of international law be justified. As Judge Kavanaugh explains in his detailed concurrence, international norms outside of those explicitly incorporated into our domestic law by the political branches are not part of the fabric of the law enforceable by federal courts after Erie. See infra, at 16-19 (Kavanaugh, J., concurring in denial of en banc rehearing). They therefore do not help courts to determine congressional intent or to recognize the wider coherence of the law. And international discourse, unlike a dictionary, is anything but a source of specific, technical, and shared linguistic meaning. Judge Williams concedes this point, characterizing international law as often “vague and deficient,” consisting of “gauzy notions” that are prone to “misuse” by nations for “political purpose[s],” and subject to official criticism by our elected representatives. Infra, at 12-13 (opinion of Williams, J.). How can sifting through such an unstable and unreliable trove of meaning be likened to opening a dictionary? How is it advisable or legitimate for courts to take on such a treacherous task, especially when the political branches possess the competency and traditional duty to do the sifting themselves by domestically incorporating international law through statute or rendering treaties self-executing? But suppose we ignore the questionable propriety of Judge Williams’ interpretive method and endeavor to apply it in this case. Ironically — and perhaps paradoxically — we likely would double-back to the same conclusion that international law does not limit the AUMF. The phrase in the AUMF on which Al-Bihani hinges his argument is “necessary and appropriate,” which he contends modifies the word “force” by prohibiting conduct not approved by international law. The closest analogy in domestic law is the phrase “necessary and proper,” which, as Judge Kava-naugh notes in his concurrence, has in its constitutional and statutory provenance been consistently interpreted to broaden rather than to constrain discretion. See, e.g., Legal Tender Cases, 79 U.S. (12 Wall.) 457, 550, 20 L.Ed. 287 (1870) (“[T]he auxiliary powers, those necessary and appropriate to the execution of other powers singly described ... are grouped in the last clause of section eight of the first article [the Necessary and Proper Clause].”) (emphasis added). Turning to international materials does not yield a different meaning. Usage of the phrase “necessary and appropriate” on the international plane grants nations wide discretion to act and does not purport to constrain them with international law. One example — among many — is U.N. Security Council Resolution 1624, which in three separate clauses calls upon states “to take all measures as may be necessary and appropriate and in accordance with their obligations under international law” to counter incitement to terrorist acts. S.C. Res. 1624, ¶¶ 1, 3, U.N. Doc. S/RES/1624 (Sept. 14, 2005) (emphasis added); see also id. pmbl. That the Security Council felt the need to append international law obligations to “necessary and appropriate”— three times, no less — indicates the phrase does not automatically incorporate such obligations. But putting aside the preceding discussion (and the odd conceptual loop it creates), I reiterate that consulting international sources in that manner is not something judges have in their interpretive toolbox. The only generally applicable role for international law in statutory interpretation is the modest one afforded by the Charming Betsy canon, which counsels courts, where fairly possible, to construe ambiguous statutes so as not to conflict with international law. See Restatement (Third) of the Foreign Relations Law of the United States § 114 (1987); see also Sampson v. Fed. Repub. of Germany, 250 F.3d 1145, 1152 (7th Cir.2001). However, Judge Williams does not appear to confine international law to such a narrow space. By including international discourse among the traditional tools available to courts when interpreting statutes, Judge Williams is not limiting the application of international law to ambiguous statutory text. Generally, a statute’s text is only ambiguous if, after “employing traditional tools of statutory construction,” a court determines that Congress did not have a precise intention on the question at issue. Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 843 n. 9, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). It is at this point — analogous to Chevron Step Two — that the Charming Betsy canon has had any application in federal courts. But Judge Williams implies that international law should be consulted in the first instance to influence interpretation at the same level as traditional interpretive tools, making its use predicate to a finding of ambiguity. This implication has the secondary effect of eviscerating the limiting principle of the Charming Betsy canon that it only exerts a negative force on the meaning of statutes, pushing them away from meanings that would conflict with international law. Courts do not apply Charming Betsy as an affirmative indicator of statutory meaning. See, e.g., Sampson, 250 F.3d at 1152-53 (holding the Charming Betsy canon does not require “federal statutes [to be] read to reflect norms of international law”); Princz v. Fed. Repub. of Germany, 26 F.3d 1166, 1174 & n. 1 (D.C.Cir.1994) (rejecting dissent’s argument that statutes must be read “consistently with international law” and must be presumed to “incorporate[ ] standards recognized under international law,” Princz, 26 F.3d at 1183 (Wald, J., dissenting)). However, under Judge Williams’ method, I see no reason why courts would be bound by this rule, since traditional interpretive sources are normally viewed as indicative of affirmative meaning. These inconsistencies with the Charming Betsy canon make clear that Judge Williams’ proposal cannot possibly be correct. If it were, it would be a mystery why American jurisprudence would even bother to enunciate an interpretive canon like the Charming Betsy. Judge Williams’ approach would make that canon vestigial, foolish even — akin to a canon limiting the use of dictionaries. Most troubling of all is the grotesque non sequitur that Congress must have intended to incorporate international law through the AUMF because it would be odd to think Congress “embrace[d]” a long history of wartime atrocity, from the Rape of Nanking to the massacre at Lidice. Judge Williams may believe that the only barrier that would hold back our nation from a descent into Nazism is an enlightened judiciary standing at the precipice, wielding international norms our polity is presumably unable to muster from within. But that belief cannot change the plain text of the AUMF, its legislative history, or the longstanding congressional practice of granting “the President a degree of discretion and freedom from statutory restriction” necessary to carry out his foreign affairs duties, Cmtiss-Wright, 299 U.S. at 320, 57 S.Ct. 216. There is no indication that the AUMF placed any international legal limits on the President’s discretion to prosecute the war and, in light of the challenge our nation faced after September 11, 2001, that makes eminent sense. Confronted with a shadowy, non-traditional foe that sueceed-ed in bringing a war to our doorstep by asymmetric means, it was (and still is) unclear how international law applies in all respects to this new context. The prospect is very real that some tradeoffs traditionally struck by the laws of war no longer make sense. That Congress wished the President to retain the discretion to recalibrate the military’s strategy and tactics in light of circumstances not contemplated by our international obligations is therefore sensible, and reflects the traditional sovereign prerogative to violate international law or terminate international.agreements. See Garcia-Mir v. Meese, 788 F.2d 1446, 1455 (11th Cir.1986) (“[T]he power of the President to disregard international law in service of domestic needs is reaffirmed.”); Restatement (Third) of the Foreign Relations Law of the United States § 339 (describing power of the President to suspend or terminate international agreements). The only way a court could reach the opposite conclusion is to go beyond the AUMF’s text, freeing it — as Judge Williams suggests — to appeal to an international meta-narrative, one activated whenever a legal issue touches on matters that strike the judge as transnational in flavor. Judges act prudently when they consciously forego opportunities for policy-making. Therefore, ignoring the text and plain meaning of a statute to privilege a more creative interpretation is the antithesis of prudence. And, in a time of war, it has the inconvenient effect of upending more than a century of our jurisprudence based on an understanding as old as the Republic: that the “conduct of foreign relations of our government is committed by the Constitution to the executive and legislative ... departments,” not to the judiciary. Oetjen v. Cent. Leather Co., 246 U.S. 297, 302, 38 S.Ct. 309, 62 L.Ed. 726 (1918). The only proper judicial role in this case is the truly modest route taken by the panel opinion in Al-Bihani. We read “necessary and appropriate” in its traditional sense, taking Congress at its word that the President is to have wide discretion. This is a modest course because the President retains the leeway to implement his authority as broadly or narrowly as he believes appropriate — consistent with international law or not — and the legislature, in turn, may add whatever limits or constraints it deems wise as the war progresses. This ensures that wartime decisions will be informed by the expertise of the political branches, stated in a clear fashion, and that the decisionmakers will be accountable to the electorate. None of those benefits accrue if the conduct of the military is subject to judicial correction based on norms of international discourse. Such an approach would place ultimate control of the war in the one branch insulated from both the battlefield and the ballot box. That would add further illegitimacy to the unpredictable and ad hoc rules judges would draw from the primordial stew of treaties, state practice, tribunal decisions, scholarly opinion, and foreign law that swirls beyond our borders. It is no comfort to the military to say, as Judge Williams does, that courts will only apply international rules they deem to possess the qualities of serious reason, evenhandedness, and practicality. Those are not judicially manageable standards. Those are buzzwords, the pleasing sound of which nearly lulls the mind into missing the vision of judicial supremacy at the heart of Judge Williams’ opinion. . Judge Kavanaugh reads this part of the government's brief differently than I do, seeing it as a conflicted argument that leaves doubt over whether the government truly means what it says. See infra, at 46-47 (Kavanaugh, J., concurring in denial of en banc rehearing). I agree the government's brief is conflicted as a general matter, but on this point I believe its claim to deference is clear. . This was, in fact, precisely the sort of deference the government received in the panel decision. .See, e.g., Jeremy Waldron, Foreign Law and the Modern Ius Gentium, 119 Harv. L.Rev. 129, 144 (2005) (proposing courts resort to norms located in a universal “ius gentium " to treat "problems that arise in our courts as though they were questions of legal science”); Jonathan Turley, Dualistic Values in the Age of International Legisprudence, 44 Hastings L.J. 185, 265, 271 (1993) (advocating courts shift "the emphasis away from determining congressional intent toward upholding international principles” and "serve a central political function in the developing transnational arena”). . See, e.g,, Ingrid Brunk Wuerth, Authorizations for the Use of Force, International Law, and the Charming Betsy Canon, 46 B.C. L.Rev. 293, 334-36, 357 (2005); Ralph G. Steinhardt, The Role of International Law as a Canon of Domestic Statutory Construction, 43 Vand. L.Rev. 1103, 1112, 1115 (1990) (positing a “presumption that Congress intends to conform its statutes to international standards” in the "absence of a clear statement of repudiation by Congress”). . See William N. Eskridge, Jr. & Philip P. Frickey, Quasi-Constitutional Law: Clear Statement Rules as Constitutional Lawmaking, 45 Vand. L.Rev. 593, 599-609 (1992) (discussing the constitutional concerns behind canons such as the constitutional avoidance canon, the rule of lenity, and the presumption in favor of judicial review). . I note the Charming Betsy canon was not invoked in the panel opinion because it is not applicable to this case. First, the relevant text of the AUMF is not ambiguous. The phrase “necessary and appropriate” is broad, but wide breadth is not tantamount to ambiguity, particularly when a phrase has a stable interpretive pedigree. Second, even if the phrase were ambiguous, the canon only applies to statutory interpretations that would violate international law. An interpretation declining to place international legal constraints on the President does not, by itself, place the United States in violation of international law. It merely affirms the President’s normal prerogative to observe or abrogate international obligations. Judge Kavanaugh also details other persuasive reasons why Charming Betsy does not apply in this case. See infra, at 31-42 (Kavanaugh, J., concurring in the denial of en banc rehearing). . Our nation has in fact established workable norms forbidding such crimes against humanity, as detailed by Judge Kavanaugh. See infra, at 12-13, 28-31 (Kavanaugh, J., concurring in denial of en banc rehearing). . That courts cannot enforce non-self-executing or non-incorporated international law against the President does not imply the United States would escape consequences of breach on the international plane. Whether to incur such consequences is part of the political calculus the President performs when deciding to disregard international obligations.
KAVANAUGH, Circuit Judge, concurring in the denial of rehearing en banc: In the 2001 Authorization for Use of Military Force, Congress authorized the President to wage war against al Qaeda and the Taliban. That war continues. At the President’s direction, the U.S. military is detaining Al-Bihani as an enemy belligerent in the ongoing conflict. Al-Bihani has asked this Court to order his release from U.S. military custody. He argues that international-law principles prohibit his continued detention. The premise of Al-Bihani’s plea for release is that international-law norms are judicially enforceable limits on the President’s war-making authority under the AUMF. Even accepting that premise, Al-Bihani cannot prevail in this case. As the panel opinion correctly concludes, Al-Biha-ni’s arguments misconstrue international law and overlook controlling federal statutes such as the Military Commissions Acts of 2006 and 2009. In any event, as the panel opinion also states, the premise of Al-Bihani’s argument is incorrect. International-law norms that have not been incorporated into domestic U.S. law by the political branches are not judicially enforceable limits on the President’s authority under the AUMF. This separate opinion explains at great length my reasons for reaching that conclusion. Al-Bihani’s invocation of international law raises two fundamental questions. First, are international-law norms automatically part of domestic U.S. law? Second, even if international-law norms are not automatically part of domestic U.S. law, does the 2001 AUMF incorporate international-law principles as judicially enforceable limits on the President’s wartime authority under the AUMF? The answer to both questions is no. First, international-law norms are not domestic U.S. law in the absence of action by the political branches to codify those norms. Congress and the President can and often do incorporate international-law principles into domestic U.S. law by way of a statute (or executive regulations issued pursuant to statutory authority) or a self-executing treaty. When that happens, the relevant international-law principles become part of the domestic U.S. law that federal courts must enforce, assuming there is a cognizable cause of action and the prerequisites for federal jurisdiction are satisfied. But in light of the Supreme Court’s 1938 decision in Erie Railroad Co. v. Tompkins, 304 U.S. 64, 58 S.Ct. 817, 82 L.Ed. 1188 (1938), which established that there is no federal general common law, international-law norms are not enforceable in federal courts unless the political branches have incorporated the norms into domestic U.S. law. None of the international-law norms cited by Al-Bihani has been so incorporated into domestic U.S. law. Second, the 2001 AUMF does not expressly or impliedly incorporate judicially enforceable international-law limits on the President’s direction of the war against al Qaeda and the Taliban. In authorizing the President to employ force, the AUMF authorizes the President to command the U.S. military to kill, capture, and detain the enemy, as Commanders in Chief traditionally have done in waging wars throughout American history. Congress enacted the AUMF with knowledge that the U.S. Constitution and other federal statutes would limit the President’s conduct of the war. But neither the AUMF’s text nor contemporaneous statements by Members of Congress suggest that Congress intended to impose judicially enforceable international-law limits on the President’s authority under the AUMF. Moreover, for three alternative reasons, the Charming Betsy canon does not authorize courts to employ international-law norms when interpreting a statute like the AUMF that broadly authorizes the President to wage war against a foreign enemy. To begin with, in the post-Nne era, the canon does not permit courts to alter their interpretation of federal statutes based on international-law norms that have not been incorporated into domestic U.S. law. Indeed, since Erie was decided, the Supreme Court has applied that canon only to support the presumption that a federal statute does not apply extraterritorially. Even if one disagrees with that initial reason for not applying Charming Betsy, however, courts may not invoke the canon against the Executive. Under basic principles of administrative law, the Executive generally has the authority to interpret ambiguous statutes within the bounds of reasonableness and, in so doing, to weigh international-law considerations as much or as little as the Executive sees fit. And even if one also disagrees with that, there is another, still narrower reason why Charming Betsy does not apply here: Courts have never applied the Charming Betsy canon against the Executive to limit the scope of a congressional authorization of war. For good reason: To the extent there is ambiguity in a statutory grant to the President of war-making authority, the President — not an international tribunal or international law — is to resolve the ambiguity in the first instance. See Dep’t of the Navy v. Egan, 484 U.S. 518, 530, 108 S.Ct. 818, 98 L.Ed.2d 918 (1988); cf. Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 842-45, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). Al-Bihani relatedly suggests that Hamdi v. Rumsfeld, 542 U.S. 507, 124 S.Ct. 2633, 159 L.Ed.2d 578 (2004), already held that the AUMF incorporates international-law norms and that courts therefore must enforce international-law limits against the President. That is incorrect: Hamdi never stated that the AUMF incorporates judicially enforceable international-law limits on the President’s authority, which of course would have been a momentous and unprecedented holding. In sum, a federal court lacks legitimate authority to interfere with the American war effort by ordering the President to comply with international-law principles that are not incorporated into statutes, regulations, or self-executing treaties. Before proceeding to the analysis of these issues, I emphasize three overarching points about the position advanced in this separate opinion. First, this opinion recognizes and reinforces the traditional roles of Congress, the President, and the Judiciary in national-security-related matters — roles endur-ingly articulated in Justice Jackson’s separate opinion in Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579, 72 S.Ct. 863, 96 L.Ed. 1153 (1952). Courts enforce constitutionally permissible constraints imposed by Congress on the President’s war powers. See Hamdan v. Rumsfeld, 548 U.S. 557, 126 S.Ct. 2749, 165 L.Ed.2d 723 (2006); Youngstown, 343 U.S. at 634-655, 72 S.Ct. 863 (Jackson, J., concurring); see generally David J. Barron & Martin S. Lederman, The Commander in Chief at the Lowest Ebb — Framing the Problem, Doctrine, and Original Understanding, 121 Harv. L.Rev. 689, 761-66 (2008). So, too, courts enforce judicially manageable limits imposed by the U.S. Constitution on the President’s war powers. See Boumediene v. Bush, 553 U.S. 723, 128 S.Ct. 2229, 171 L.Ed.2d 41 (2008); Hamdi 542 U.S. 507, 124 S.Ct. 2633. But courts may not interfere with the President’s exercise of war powers based on international-law norms that the political branches have not seen fit to enact into domestic U.S. law. Second, the limited authority of the Judiciary to rely on international law to restrict the American war effort does not imply that the political branches should ignore or disregard international-law norms. The principles of the international laws of war (and of international law more generally) deserve the respect of the United States. Violating international-law norms and breaching international obligations may trigger serious consequences, such as subjecting the United States to sanctions, undermining U.S. standing in the world community, or encouraging retaliation against U.S. personnel abroad. Therefore, Congress and the President are often well-advised to take account of international-law principles when considering potential legislation or treaties. And even when international-law norms have not been incorporated into domestic U.S. law, the Executive Branch, to the extent permissible under its constitutional and statutory authority, is often wise to pay close attention to those norms as a matter of sound policy, international obligation, or effective foreign relations. See, e.g., Harold Hongju Koh, Legal Adviser, U.S. Department of State, The Obama Administration and International Law: Address at the Annual Meeting of the American Society of International Law (Mar. 25, 2010); John B. Bellinger III, Legal Adviser, U.S. Department of State, Testimony Before the Senate Committee on Foreign Relations (April 15, 2008), reprinted in part in Digest of United States Practice In International Law 2008, at 887-88 (Elizabeth R. Wilcox ed.); Letter from Gen. Colin L. Powell to Sen. John McCain (Sept. 13, 2006), reprinted at 152 Cong. Rec. S10,412 (daily ed. Sept. 28, 2006). But in our constitutional system of separated powers, it is for Congress and the President — not the courts — to determine in the first instance whether and how the United States will meet its international obligations. When Congress and the President have chosen not to incorporate international-law norms into domestic U.S. law, bedrock principles of judicial restraint and separation of powers counsel that courts respect that decision. Third, consistent with that constitutional division of authority, Congress has enacted a significant body of legislation to prohibit certain wartime actions by the Executive and military that contravene American values. For example, Congress has adopted a detailed and extensive Uniform Code of Military Justice, which governs many aspects of military conduct. See 10 U.S.C. §§ 801-946. Congress also has passed separate laws banning genocide and war crimes, including laws criminalizing grave breaches of the Geneva Conventions (such as rape, torture, and murder). See, e.g., 18 U.S.C. §§ 1091, 2441. In addition, acting pursuant to congressional authorization, the Executive Branch has promulgated numerous legally binding rules that regulate wartime conduct of the military. See, e.g., Enemy Prisoners of War, Retained Personnel, Civilian Internees and Other Detainees, Army Reg. 190-8, § 1 — 1(b) (Oct. 1, 1997). Those laws, along with many other statutes and regulations, together constitute a comprehensive body of domestic U.S. laws of war. In his thoughtful opinion in connection with the denial of rehearing, Judge Williams says that it “would be an odd member of Congress who supposed that in authorizing the use of military force he was embracing uses equivalent to all such uses that have ever occurred: think Nanking 1937-38; Katyn 1940; Lidice 1942; My Lai 1968.” Williams Op. at 54. I agree entirely with Judge Williams on that point, but not because I believe Congress intended for U.S. courts to enforce international-law norms against the Executive. Rather, when Congress authorized war in 2001, it did so knowing that domestic U.S. law already prohibited a variety of improper wartime conduct. Judge Williams’ worrisome hypotheticals are thus already taken care of — by the domestic U.S. laws of war — and do not support his suggestion that the AUMF incorporates international-law norms. Notably, Judge Williams points to no examples of violations of international law that would be contrary to fundamental American values but that are not already independently prohibited by domestic U.S. law. There is a good deal of overlap between the international laws of war and domestic U.S. laws regulating war. When there is divergence, however, Congress and the President — not the courts — have the authority in the first instance to decide whether and how to conform U.S. law to international law. I Four categories of law are relevant to this case: federal statutes; self-executing treaties made by the President with the concurrence of two-thirds of the Senate; non-self-executing treaties made by the President with the concurrence of two-thirds of the Senate; and customary international law. Those four categories do not share the same status in U.S. law. As I will explain, statutes and self-executing treaties are domestic U.S. law and thus enforceable in U.S. courts. By contrast, non-self-executing treaties and customary international law are not domestic U.S. law. See Medellín v. Texas, 552 U.S. 491, 128 S.Ct. 1346, 170 L.Ed.2d 190 (2008); Sosa v. Alvarez-Machain, 542 U.S. 692, 124 S.Ct. 2739, 159 L.Ed.2d 718 (2004). Only when international-law principles are incorporated into a statute or a self-executing treaty do they become domestic U.S. law enforceable in U.S. courts. In this case, none of the purported international-law principles cited by Al-Bihani has been incorporated into a statute or self-executing treaty. Those principles are therefore not part of the domestic law of the United States and, on their own, do not authorize a U.S. court to order Al-Bihani’s release from U.S. military detention. A In our constitutional system, international-law norms may achieve the status of domestic U.S. law through two mechanisms: incorporation into a statute (or legally binding executive regulation adopted pursuant to a statute) or incorporation into a self-executing treaty. First, international-law norms may be incorporated into legislation approved by a majority in both Houses of Congress and signed by the President (or enacted over a presidential veto, or by operation of the Constitution’s ten-day rule). See U.S. Const, art. I, § 7. The important role Congress plays in this sphere is apparent from the text of the Constitution, which specifically authorizes Congress to “define and punish ... Offences against the Law of Nations.” Id. art. I, § 8, cl. 10. The delegates to the Constitutional Convention expressly assigned that power to Congress because, as Gouverneur Morris aptly noted at the Convention, international-law principles are “often too vague and deficient to be a rule” without implementing legislation. 2 The Records of the Federal Convention of 1787, at 615 (Max Farrand ed., rev. ed.1937); see also United States v. Smith, 18 U.S.(5 Wheat.) 153, 159, 5 L.Ed. 57 (1820) (international law “cannot, with any accuracy, be said to be completely ascertained and defined in any public code re-cognised by the common consent of nations”). Consistent with that constitutionally assigned role, Congress sometimes enacts statutes to codify international-law norms derived from non-self-executing treaties or customary international law, or to fulfill international-law obligations. The Foreign Sovereign Immunities Act of 1976 is a good example of that kind of legislation. The Act governs federal courts’ jurisdiction to entertain suits against foreign nations. See 28 U.S.C. §§ 1602-1611. As the Supreme Court has recognized, “one of the primary purposes of the FSIA was to codify ... extant international law.” Samantar v. Yousuf, — U.S.-, 130 S.Ct. 2278, 2289, 176 L.Ed.2d 1047 (2010). Likewise, the War Crimes Act criminalizes certain conduct — including torture, rape, and hostage-taking — committed in war by or against U.S. nationals or members of the U.S. Armed Forces. The Act provides that this conduct “constitutes a grave breach of common Article 3” of the 1949 Geneva Conventions. See 18 U.S.C. § 2441(c)(3), (d)(1). Similarly, the Genocide Convention Implementation Act of 1987 criminalizes participation in genocide and thereby implements a non-self-executing treaty to which the United States is a party. See id. §§ 1091-1093; Convention on the Prevention and Punishment of the Crime of Genocide, adopted Dec. 9, 1948, S. TREATY DOC. NO. 81-15; see also Demjanjuk v. Meese, 784 F.2d 1114, 1116 (D.C.Cir.1986) (Bork, J., in chambers) (Genocide Convention is not self-executing). Congress also has passed several laws designed to implement certain aspects of the international Convention Against Torture, a non-self-executing treaty to which the United States is a party. See Convention Against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, adopted Dec. 10, 1984, S. Treaty Doc. No. 100-20; Wang v. Ashcroft, 320 F.3d 130, 140 (2d Cir.2003). For example, the Torture Victim Protection Act of 1991 creates a civil cause of action to recover damages for torture committed by foreign officials, “in part to fulfill the Convention’s mandate that ratifying nations take action to ensure that torturers are held legally accountable for their actions.” Price v. Socialist People’s Libyan Arab Jamahiriya, 294 F.3d 82, 92 (D.C.Cir.2002); see 18 U.S.C. § 1350 note. Likewise, the federal criminal torture statute establishes criminal penalties for U.S. nationals (and non-U.S. persons present in the United States) who commit or conspire to commit torture outside U.S. territory; that statute fulfills U.S. obligations under Articles 4 and 5 of the Convention. 18 U.S.C. §§ 2340-2340A; see Renkel v. United States, 456 F.3d 640, 644 (6th Cir.2006). When incorporating international-law norms into domestic U.S. law, Congress sometimes simply enacts statutes that refer generieally to “international law” (or some variation thereof) without further defining what international law requires. For example, federal piracy statutes permit the capture and forfeiture of vessels used for, and the imprisonment of individuals who commit, acts of “piracy as defined by the law of nations.” 18 U.S.C. § 1651; 33 U.S.C. §§ 384-385; see Ex parte Quirin, 317 U.S. 1, 29, 63 S.Ct. 1, 87 L.Ed. 3 (1942). Similarly, Congress has authorized the President to use military force to detain foreign vessels at American ports when such action is permitted “by the law of nations or the treaties of the United States.” 22 U.S.C. § 462. It has also empowered the President to impose sanctions on foreign countries that use chemical or biological weapons “in violation of international law.” Id. §§ 5604-5605. In addition, Article 21 of the Uniform Code of Military Justice allows military commissions to the extent permitted by statute or the “law of war.” 10 U.S.C. § 821; see Hamdan v. Rumsfeld, 548 U.S. 557, 593, 126 S.Ct. 2749, 165 L.Ed.2d 723 (2006) (Congress “preserved what power, under the Constitution and the common law of war, the President had had before 1916 to convene military commissions — with the express condition that the President and those under his command comply with the law of war”). Congress likewise has repeatedly directed Executive agencies to comply with “general” or “generally recognized” “principles of international law” when administering statutes that involve activities in international waters. See, e.g., 10 U.S.C. § 113 note (Sunken Military Craft, § 1406(b)) (protection of sunken military vessels); 16 U.S.C. § 1435(a) (management of national marine sanctuaries); 30 U.S.C. § 1421 (issuance of permits for deepwater mining operations); 42 U.S.C. § 9119 (issuance of permits for ocean thermal energy conversion facilities). Second, in addition to being incorporated into a statute (or executive regulation adopted pursuant thereto), international-law principles may become part of domestic U.S. law by means of a self-executing treaty that is made by the President with the concurrence of two-thirds of the Senate. See U.S. Const, art. II, § 2, cl. 2; Medellín, 552 U.S. at 505 n. 2, 128 S.Ct. 1346; Foster v. Neilson, 27 U.S.(2 Pet.) 253, 314, 7 L.Ed. 415 (1829). A self-executing treaty is one that “reflect[s] a determination by the President who negotiated it and the Senate that confirmed it that the treaty has domestic effect.” Medellín, 552 U.S. at 521, 128 S.Ct. 1346. By contrast, a treaty is non-self-executing when it “reads like a compact between independent nations that depends for the enforcement of its provisions on the interest and the honor of the governments which are parties to it.” Id. at 508-09, 128 S.Ct. 1346 (quoting Head Money Cases, 112 U.S. 580, 598, 5 S.Ct. 247, 28 L.Ed. 798 (1884)) (internal quotation marks omitted). Numerous bilateral treaties — agreements between the United States and one other nation — are self-executing. For example, the United States has entered into many bilateral Friendship, Commerce, and Navigation treaties, which define the civil, property, and commercial rights each treaty country will afford to nationals of the other. Courts have routinely held such treaties to be self-executing. See Medellin, 552 U.S. at 521, 128 S.Ct. 1346 (“we have held that a number of the ‘Friendship, Commerce, and Navigation’ Treaties ... are self-executing”); Kolovrat v. Oregon, 366 U.S. 187, 191, 196, 81 S.Ct. 922, 6 L.Ed.2d 218 (1961) (Treaty of Commerce between United States and Serbia enforceable in U.S. court); Clark v. Allen, 331 U.S. 503, 508, 517, 67 S.Ct. 1431, 91 L.Ed. 1633 (1947) (Treaty of Friendship, Commerce, and Consular Rights between United States and Germany enforceable in U.S. court); Asakura v. City of Seattle, 265 U.S. 332, 341, 44 S.Ct. 515, 68 L.Ed. 1041 (1924) (Treaty of Commerce and Navigation between United States and Japan “operates of itself without the aid of any legislation” and “will be applied and given authoritative effect by the courts”); McKesson Corp. v. Islamic Republic of Iran, 539 F.3d 485, 488 (D.C.Cir.2008) (Treaty of Amity, Economic Relations, and Consular Rights between United States and Iran, “like other treaties of its kind, is self-executing”). Similarly, bilateral extradition treaties are ordinarily considered self-executing. See, e.g., Cheung v. United States, 213 F.3d 82, 95 (2d Cir.2000). Courts have been somewhat more reluctant to find multilateral treaties self-executing. See, e.g., Andrea Bianchi, International Law and U.S. Courts: The Myth of Lohengrin Revisited, 15 Eur. J. Int’l L. 751, 758 (2004); Curtis A. Bradley, International Delegations, the Structural Constitution, and Non-Self-Execution, 55 Stan. L.Rev. 1557, 1588 & n. 147 (2003). As one court explained, when a multilateral treaty is ratified by many nations, “some of which do not recognize treaties as self-executing,” it is difficult for courts to “ascribe to the language of the treaty any common intent that the treaty should of its own force operate as the domestic law of the ratifying nations.” United States v. Postal, 589 F.2d 862, 878 (5th Cir.1979). However, a multilateral treaty still may be self-executing if its terms indicate that the President and Senate so intended. An example is the Warsaw Convention, a treaty entered into by President Franklin Roosevelt with the concurrence of the U.S. Senate in 1934. It governs the liability of air carriers for passenger injuries and lost cargo. See Convention for the Unification of Certain Rules Relating to International Transportation by Air, opened for signature Oct. 12, 1929, 49 Stat. 3000. The Supreme Court has held that “no domestic legislation is required to give the [Warsaw] Convention the force of law in the United States.” Trans World Airlines, Inc. v. Franklin Mint Corp., 466 U.S. 243, 252, 104 S.Ct. 1776, 80 L.Ed.2d 273 (1984); see, e.g., El Al Israel Airlines, Ltd. v. Tsui Yuan Tseng, 525 U.S. 155, 176, 119 S.Ct. 662, 142 L.Ed.2d 576 (1999); Curtin v. United Airlines, Inc., 275 F.3d 88, 90 (D.C.Cir.2001). Some other multilateral treaties also have been regarded as self-executing, such as the Hague Convention on the Taking of Evidence Abroad in Civil or Commercial Matters, the General Inter-American Convention for Trade Mark and Commercial Protection, and the Vienna Convention on Consular Relations. See Société Nationale Industrielle Aérospatiale v. U.S. Dist. Ct. for the S. Dish of Iowa, 482 U.S. 522, 533, 107 S.Ct. 2542, 96 L.Ed.2d 461 (1987); Bacardi Corp. of America v. Domenech, 311 U.S. 150, 161, 61 S.Ct. 219, 85 L.Ed. 98 (1940); Gandara v. Bennett, 528 F.3d 823, 828 (11th Cir. 2008). B By contrast, international-law principles found in non-self-executing treaties and customary international law, but not incorporated into statutes or self-executing treaties, are not part of domestic U.S. law. The Supreme Court has squarely held that non-self-executing treaties “are not domestic law.” Medellín, 552 U.S. at 505, 128 S.Ct. 1346 (quotation omitted). Therefore, “responsibility for transforming an international obligation arising from a non-self-executing treaty into domestic law falls to Congress.” Id. at 525-26, 128 S.Ct. 1346. The Supreme Court has likewise indicated that customary international law is not automatically part of domestic U.S. law. See Sosa, 542 U.S. 692, 124 S.Ct. 2739. Customary international law is said to arise from the “general and consistent practice of states followed by them from a sense of legal obligation.” Restatement (Third) of Foreign Relations Law of the United States § 102(2) (1987). It is a kind of international common law. It does not result from any of the mechanisms specified in the U.S. Constitution for the creation of U.S. law. For that reason, although norms of customary international law may obligate the United States internationally, they are not part of domestic U.S. law. Customary-international-law norms become part of domestic U.S. law only if the norms are incorporated into a statute or self-executing treaty. To be sure, there was a time when U.S. courts stated that customary international law was “part of our law” so that “where there is no treaty, and no controlling executive or legislative act or judicial decision, resort must be had to the customs and usages of civilized nations; and, as evidence of these, to the works of jurists and commentators.” The Paquete Habana, 175 U.S. 677, 700, 20 S.Ct. 290, 44 L.Ed. 320 (1900). But that oft-quoted statement reflected the notion, common in the early years of the Nation but now discredited, that international law was part of the general common law that federal courts could apply. See Sosa, 542 U.S. at 714-15, 124 S.Ct. 2739; Erie R.R. Co. v. Tompkins, 304 U.S. 64, 79, 58 S.Ct. 817, 82 L.Ed. 1188 (1938) (historically, the common law was viewed as “a transcendental body of law outside of any particular State but obligatory within it unless and until changed by statute”) (quotation omitted); Curtis A. Bradley & Jack L. Goldsmith, Customary International Law as Federal Common Law: A Critique of the Modem Position, 110 Harv. L.Rev. 815, 849 (1997) (the “statement in The Paquete Habana that CIL [customary international law] was ‘part of our law1 ” was “made under the rubric of general common law” and “did not mean that CIL had the status of federal law”); Ernest A. Young, Sorting Out the Debate over Customary International Law, 42 Va. J. Int’l L. 365, 393-94 (2002) (“as virtually all participants in the customary law debate agree,” before Erie, international law “had the status of ‘general’ law: neither state nor federal”); Bradford R. Clark, Federal Common Law: A Stmctural Reinterpretation, 144 U. Pa. L.Rev. 1245, 1279-81 & n. 169 (1996) (before Erie, international law, including the laws governing war, “operated as a set of background rules that courts applied in the absence of any binding sovereign command to the contrary”); John F. Manning, Textualism and the Equity of the Statute, 101 Colum. L.Rev. 1, 99 n. 382 (2001) (“Because courts applying the law of nations believed that they were merely implementing a pre-existing body of customary law, this decisionmaking process was not conceived of as lawmaking per se.”). But as decided by the Supreme Court in its landmark Erie decision in 1938, the view that federal courts may ascertain and enforce international-law norms as part of the general common law is fundamentally inconsistent with a proper understanding of the role of the Federal Judiciary in our constitutional system. In Erie, the Supreme Court famously held that there is no general common law enforceable by federal courts. Erie, 304 U.S. at 78, 58 S.Ct. 817. The Court said that “law in the sense in which courts speak of it today does not exist without some definite authority behind it.” Id. at 79, 58 S.Ct. 817 (quotation omitted). Erie means that, in our constitutional system of separated powers, federal courts may not enforce law that lacks a domestic sovereign source. Erie “requires federal courts to identify the sovereign source for every rule of decision,” and the “appropriate ‘sovereigns’ under the U.S. Constitution are the federal government and the states.” Bradley & Goldsmith, Customary International Law, 110 Harv. L.Rev. at 852; see also Anthony J. Bellia Jr., State Courts and the Making of Federal Common Law, 153 U. Pa. L.Rev. 825, 891 (2005) (“the rise of positivistic legal thought led courts to conclude that all law ... must be attributable to a sovereign source”); Louise Weinberg, The Curious Notion that the Rules of Decision Act Blocks Supreme Federal Common Law, 83 NW. U.L. REV. 860, 867 (1989) (“post-Erie positivism has cleansed American courts of law lacking an identifiable sovereign source”). Some respected scholars have asserted that even though Erie did away with the idea of federal general common law, principles of customary international law may still be recognized as federal common law by federal courts. See, e.g., Harold Hongju Koh, Is International Law Really State Law?, Ill HaRV. L.Rev. 1824, 1835 (1998). But that notion is very difficult to square with Erie — as other leading scholars have maintained. Indeed, “[cjourts and scholars generally agree that federal common law must be authorized in some fashion by the Constitution or a federal statute.” Bradley & Goldsmith,