LEWIS A. KAPLAN, District Judge.

On September 11, 2001, the al-Qaeda terrorist network attacked multiple targets in the United States with hijacked commercial airliners, killing approximately 3,000 people. A week later, Congress enacted the Authorization for Use of Military Force (the "AUMF"),1 which empowered President Bush to use all necessary and appropriate force against those nations, organizations, and persons responsible for the attacks and those who harbored such organizations or persons.

Nearly twelve years later, the hostilities continue. Presidents Bush and Obama have asserted the right to place certain individuals in military detention, without trial, in furtherance of their authorized use of force. Substantial litigation has ensued over the scope of presidential military detention authority — that is, whom did Congress authorize the President to detain when it passed the AUMF?

On December 31, 2011, President Obama signed into law the National Defense Authorization Act for Fiscal Year 2012.2 Section 1021 of that statute, which fits on a single page, is Congress' first — and, to date, only — foray into providing further clarity on that question. Of particular importance for our purposes, Section 1021(b)(2) appears to permit the President to detain anyone who was part of, or has substantially supported, al-Qaeda, the Taliban, or associated forces.

The controversy over Section 1021 was immediate. The government contends that Section 1021 simply reaffirms authority that the government already had under the AUMF, suggesting at times that the statute does next to nothing at all. Plaintiffs take a different view. They are journalists and activists who allegedly fear that the government may construe their work as having substantially supported al-Qaeda, the Taliban, or associated forces. They contend that Section 1021 is a dramatic expansion of the President's military detention authority, supposedly authorizing the military, for the first time, to detain American citizens on American soil. As one group of amici has noted, "[r]arely has a short statute been subject to more radically different interpretations than Section 1021."3

Plaintiffs brought this action shortly after the statute was enacted. They sought an injunction barring enforcement of Section 1021 and a declaration that it violates, among other things, their rights under the First and Fifth Amendments to the United States Constitution. The district court agreed and entered a permanent injunction restraining detention pursuant to Section 1021(b)(2). It is that decision that we review here.

We conclude that plaintiffs lack standing to seek preenforcement review of Section 1021 and vacate the permanent injunction. The American citizen plaintiffs lack standing because Section 1021 says nothing at all about the President's authority to detain American citizens. And while Section 1021 does have a real bearing on those who are neither citizens nor lawful resident aliens and who are apprehended abroad, the non-citizen plaintiffs also have failed to establish standing because they have not shown a sufficient threat that the government will detain them under Section 1021. Accordingly, we do not address the merits of plaintiffs' constitutional claims.

I. Background

Prior to the passage of Section 1021, a number of federal judges reached divergent conclusions about the scope of AUMF detention authority. To appreciate what Congress did and did not resolve in passing Section 1021, one must understand the nature of this debate. We thus describe the history of the litigation over AUMF detention authority in some detail.

A. The AUMF

The AUMF, enacted on September 18, 2001, provides:

President Bush ordered the United States military to Afghanistan to subdue al-Qaeda and the Taliban regime known to support it. Soon thereafter, President Bush began to hold certain individuals in military detention as "enemy combatants," many of them at the United States Naval Base in Guantánamo Bay, Cuba.5

B. The Citizen and Domestic Capture Cases: Hamdi, Padilla, and al-Marri

As one scholar has noted, the litigation regarding the scope of executive detention authority may be divided into two "waves": (1) litigation from 2002 to 2008 regarding three individuals who were held as enemy combatants in military detention within the territorial United States, and (2) litigation from 2008 to the present concerning Guantánamo detainees.6 The first category comprises the cases of Yaser Esam Hamdi, Jose Padilla, and Ali Saleh Kahlah al-Marri.

1. Hamdi

Hamdi, then an American citizen, was in Afghanistan in the fall of 2001, where he allegedly was armed and affiliated with a Taliban military unit that had provided him weapons training.7 He was apprehended when that unit surrendered after a battle.8 After entering military detention within the United States, a habeas corpus petition was filed on his behalf, alleging inter alia that his detention violated the Non-Detention Act of 1971, which provides, "No citizen shall be imprisoned or otherwise detained by the United States except pursuant to an Act of Congress."9

Although the Supreme Court in June 2004 remanded Hamdi's case to allow him to challenge his status as an enemy combatant, it upheld the government's authority to detain a properly designated enemy combatant in Hamdi v. Rumsfeld,10 when "five Members of the Court recognized that detention of individuals who fought against the United States in Afghanistan `for the duration of the particular conflict in which they were captured, is so fundamental and accepted an incident to war as to be an exercise of the "necessary and appropriate force" Congress has authorized the President to use'" by the AUMF.11

In so doing, a four Justice plurality12 noted that "[t]he legal category of enemy combatant has not been elaborated upon in great detail" and that "[t]he permissible bounds of the category will be defined by the lower courts as subsequent cases are presented to them."13 It nevertheless concluded that the AUMF "clearly and unmistakably" authorized detaining at least those who were "part of or supporting forces hostile to the United States or coalition partners in Afghanistan and who engaged in an armed conflict against the United States there."14 Thus, the plurality reasoned that, if the government's allegations were correct, Hamdi's detention did not violate the Non-Detention Act because the AUMF itself constituted the requisite "Act of Congress."15 To the extent Hamdi identified constitutional concerns with the military detention of American citizens generally, the plurality concluded that there was "no bar to this Nation's holding one of its own citizens as an enemy combatant."16 Nevertheless, the plurality suggested that this detention authority was not boundless and that detention pursuant to it could not be indefinite. Rather, "based on longstanding law-of-war principles," the plurality construed the AUMF "to include the authority to detain for the duration of the relevant conflict."17 Justice Thomas wrote separately and provided a fifth vote for upholding authority to detain Hamdi under the AUMF, but rejected any limitations, derived from the laws of war, on the duration of the detention authority.18

The four remaining Justices dissented from the conclusion that Hamdi could be detained, reasoning inter alia that the AUMF did not constitute sufficiently clear authorization of his detention to satisfy the Non-Detention Act.19 Justice Scalia, joined by Justice Stevens, would have held further that the government was without constitutional power to detain Hamdi militarily absent congressional suspension of the writ of habeas corpus.20

2. Padilla

Padilla, also an American citizen, was apprehended at Chicago's O'Hare International Airport in May 2002 after allegedly receiving training from al-Qaeda in Afghanistan, becoming involved in a plan to detonate a "dirty bomb" here, and returning to the United States to conduct reconnaissance and facilitate attacks by al-Qaeda.21

In December 2003 — prior to Hamdi — this Court held that because Padilla was an American citizen arrested on domestic soil away from a zone of combat, his military detention violated the Non-Detention Act and could not be justified by the President's Article II war powers.22 The Supreme Court reversed our decision on procedural grounds on the day it decided Hamdi but did not reach the lawfulness of Padilla's detention.23

Following the Supreme Court's reversal of our Padilla ruling, a new habeas petition was filed on his behalf. The Fourth Circuit in 2005 concluded that Padilla was lawfully detained under the reasoning of Hamdi because it became known that he had been "armed and present in a combat zone during armed conflict between al Qaeda/Taliban forces and the armed forces of the United States" while in Afghanistan prior to his return to the United States.24 Although Padilla had been apprehended in the United States, the Fourth Circuit concluded that Hamdi had not relied on the place of capture.25 The government subsequently indicted Padilla and transferred him to civilian criminal custody. His petition for certiorari was denied.26

3. Al-Marri

The Fourth Circuit again considered the scope of military detention authority in the case of al-Marri, a Qatari national apprehended in the United States while he was lawfully residing here.27 Al-Marri allegedly was a "sleeper agent" who had met Osama Bin Laden, was trained by al-Qaeda, and had been sent to the United States to facilitate terrorist activities here.28 Unlike Padilla and Hamdi, however, the government did not allege that al-Marri had stood alongside armed forces hostile to the United States or had been present in a combat zone during hostilities.29

A splintered en banc Fourth Circuit concluded in July 2008 that the executive had authority to detain al-Marri as an enemy combatant, assuming that the government's allegations were true.30 While each offered a different definition of those subject to detention, the three principal opinions which voted in favor of this general proposition gave significant weight to the fact that, if the government's allegations were correct, al-Marri was little different from the 9/11 hijackers themselves, short of succeeding in the plot.31 The judges who took the contrary view concluded that al-Marri was a civilian and therefore could not properly be detained militarily under traditional principles of the laws of war.32 The key question for them was whether he had affiliated "with the military arm of an enemy nation."33

The Supreme Court granted certiorari,34 but then vacated the decision below as moot when the newly elected Obama administration indicted al-Marri and sought to transfer him to civilian criminal custody.35

C. The Guantánamo Cases

Meanwhile, Congress and the courts were engaging in a dialogue over a more basic question regarding the Guantánamo detainees — whether they had any right to petition for habeas corpus at all.36 This culminated in June 2008 with Boumediene v. Bush, which held that the Guantánamo detainees had constitutional habeas rights and that the procedures that Congress and the administration had provided were not an adequate substitute.37

1. Activity Pre-Boumediene

In July 2004, shortly after Hamdi, the government created Combatant Status Review Tribunals ("CSRTs") to determine whether the Guantánamo detainees were enemy combatants, which the Department of Defense then defined to mean "an individual who was part of or supporting Taliban or al Qaeda forces, or associated forces that are engaged in hostilities against the United States or its coalition partners. This includes any person who has committed a belligerent act or has directly supported hostilities in aid of enemy armed forces."38

Congress did not endorse this definition or otherwise speak directly to the scope of detention authority during this period. It codified the CSRT process in the Detainee Treatment Act of 2005, but that statute did not explain who could be detained.39 The Military Commissions Act of 2006 defined the concept of an "unlawful enemy combatant," but only with respect to eligibility for trial by the military commissions created by that act, not to AUMF detention authority.40

2. Judicial Consideration post-Boumediene

Absent clarity from Congress, Boumediene opened the gates to judicial evaluation of the scope of executive detention authority for Guantánamo detainees. On remand from the Supreme Court, Judge Leon of the D.C. district court in the fall of 2008 declined to follow any of the approaches set forth in al-Marri and instead adopted the government's prior 2004 CSRT definition, concluding that it was consistent with the AUMF and the Constitution.41

a. March 2009 Memo

On March 13, 2009, the new administration, in a memorandum to the D.C. district court (the "March 2009 Memo" or the "Memo"),42 "refin[ed]" the government's position regarding its detention authority for "those persons who are now being held at Guantánamo Bay."43 Relying on the Hamdi plurality opinion, the Memo asserted that the scope of executive detention authority "is necessarily informed by principles of the laws of war," as these principles "inform the understanding of what is `necessary and appropriate'" under the AUMF.44 With this predicate, the Memo declared that the government, in addition to being able to detain individuals themselves responsible for the attacks, had the authority

It stated further that "[i]t is neither possible nor advisable" to identify what these terms mean in the abstract.46 Nevertheless, the March 2009 Memo said that the inquiry with regard to whether an individual is "part of" the enumerated forces may depend on either "a formal or functional analysis of the individual's role."47 With regard to "associated forces," it observed that "many different private armed groups" fought alongside al-Qaeda and the Taliban in Afghanistan and therefore declared the authority to detain individuals who "in analogous circumstances in a traditional international armed conflict ... would be detainable under principles of co-belligerency."48 Finally, it said that the term "substantial support" does not justify detaining "those who provide unwitting or insignificant support" to the identified organizations.49 But, "[u]nder a functional analysis, individuals who provide substantial support to al-Qaida forces in other parts of the world may properly be deemed part of al-Qaida itself."50 Moreover, "[s]uch activities may also constitute the type of substantial support that, in analogous circumstances in a traditional international armed conflict, is sufficient to justify detention."51 In any event, the March 2009 Memo took the view that "the AUMF is not limited to persons captured on the battlefields of Afghanistan" nor to those "directly participating in hostilities."52

b. District Court Reaction

District of Columbia district court reactions to the March 2009 Memo were mixed. Judges uniformly accepted the government's "part of" test but expressed considerable skepticism about "substantial support."53 One opinion adopted the government's position, but only by reading "substantial support" narrowly to permit detention of those "effectively part of the armed forces of the enemy."54 In what became the majority view in the D.C. district court, another went one step further and rejected the government's reliance on "substantial support" and "directly support[ing] hostilities" altogether, concluding that detention on such grounds was unsupported either by domestic law or the laws of war.55

c. Al-Bihani

These decisions set the stage for the D.C. Circuit's central ruling on the scope of AUMF detention authority, Al-Bihani v. Obama.56 Petitioner Al-Bihani carried a weapon and was a cook for a unit that fought alongside the Taliban.57 He contended that his detention was inconsistent with the laws of war and thus not authorized as "necessary and appropriate" under the AUMF.58 The majority opinion rejected the notion that the laws of war limit the government's AUMF authority at all — even though the government agreed with Al-Bihani on that point.59 Taking the view that the "the government's detention authority logically covers a category of persons no narrower than is covered by its military commission authority," the majority concluded that Al-Bihani was properly detained because he fell within the latter standard, which Congress had set forth in the Military Commissions Acts of 2006 and 2009.60 That is, the majority held that AUMF detention authority "includes those who are part of forces associated with Al Qaeda or the Taliban or those who purposefully and materially support such forces in hostilities against U.S. Coalition partners."61

While focusing on this "purposeful and material support" standard, the majority's discussion seemed generally supportive of the government's "substantial support" standard as well. The majority stated that Al-Bihani was detained lawfully under either the CSRT definition or the government's modified "substantial support" definition.62 Moreover, it later noted that Al-Bihani "both [was] part of and [had] substantially supported enemy forces" and, without exploring the bounds of these concepts, "recognize[d] that both prongs are valid criteria that are independently sufficient to satisfy the [detention] standard."63

d. Subsequent D.C. Circuit Case Law

Further decisions by the D.C. Circuit followed the principle that the AUMF authorized detention not only of those who are "part of" al-Qaeda and the Taliban but also those who "purposefully and materially support" such forces.64 Notably, however, the D.C. Circuit has not had occasion to develop further the contours of the "support" prong, apparently because the government appears rarely to rely on it. Rather, in numerous cases before the D.C. Circuit since Al-Bihani, the government has relied on a theory that the detainee was "part of" al-Qaeda, the Taliban, or associated forces.65 In fact, in Bensayah v. Obama,66 a case argued before but decided after Al-Bihani, the government specifically foreswore reliance on any support justification for detention.67 It did so despite the facts that (1) support was the sole ground on which the district court had relied in finding Bensayah detainable, and (2) the March 2009 Memo had cited that district court decision as its one example of when "substantial support" might apply.68 Moreover, the government dropped reliance on a "purposeful and material support" theory in Salahi v. Obama.69

D. The 2012 NDAA

It was in this context that the 2012 NDAA was enacted on December 31, 2011. Section 1021 of that statute provides in relevant part:

But it is useful to set out the history of this provision, as it may shed light on its proper construction.

An initial version of this section was reported by the House Armed Services Committee in May 2011.71 It affirmed that the United States "is engaged in an armed conflict with al-Qaeda, the Taliban, and associated forces" and that the President has the authority to use force against those who (A) are "part of, or are substantially supporting, al-Qaeda, the Taliban, or associated forces" or (B) "have engaged in hostilities or have directly supported hostilities in aid of a nation, organization, or person described in subparagraph (A)."72 Such use of force, the bill provided, includes the power to detain such persons until the termination of hostilities.73 The committee report stated the following about the provision:

The Senate Armed Services Committee developed a different version of this section, Section 1031 of S. 1253, which was reported out of committee on June 22, 2011.75 Subsections (a)-(c) of that section were similar to subsections (a)-(c) of the later enacted Section 1021.76 Section 1031 of S. 1253, however, included a "limitation" stating that the detention authority "does not extend to the detention of citizens or lawful resident aliens of the United States on the basis of conduct taking place within the United States except to the extent permitted by the Constitution."77 The committee report stated:

The detainee sections of S. 1253, including but not limited to Section 1031, encountered some opposition from senators and the administration.79 After various consultations, the Senate Armed Services Committee reported a revised version on November 15, 2011, as S. 1867. Section 1031(a)(d) of S. 1867 was identical to the ultimately enacted Section 1021(a)(d).80 In particular, S. 1867 removed the limitation regarding detention of citizens and lawful resident aliens based on domestic conduct. It also added a provision stating, "Nothing in this section is intended to limit or expand the authority of the President or the scope of the [AUMF]."81 On November 17, the administration issued a Statement of Administration Policy which stated that Section 1031 was unnecessary because the authority it attempted to codify already existed and expressed concern about potential unintended consequences from legislative action in this area.82

In ensuing floor debates, a number of senators raised concerns that Section 1031 provided new authority to the President to detain American citizens indefinitely, with particular concern about citizens captured domestically.83 Senator Dianne Feinstein unsuccessfully proposed an amendment that would have provided: "The authority described in this section for the [military] to detain a person does not include the authority to detain a citizen of the United States without trial until the end of the hostilities."84

Senator Feinstein prevailed in putting forth a second proposal, however, a so-called "compromise amendment"85 that ultimately became Section 1021(e) and read, as enacted: "Nothing in this section shall be construed to affect existing law or authorities relating to the detention of United States citizens, lawful resident aliens of the United States, or any other persons who are captured or arrested in the United States."86 In advancing this proposal, Senator Feinstein observed that the dispute over Section 1031 boiled down to "different interpretations of what the current law is."87 Specifically, she noted that

Senator Feinstein went on to state that, through her second proposed amendment, the two camps would agree to disagree:

Senator Carl Levin, a principal sponsor of the bill and opponent of Senator Feinstein's first proposed amendment, supported her second proposal, stating:

Other senators, on both sides of the debate, also voiced their support and characterized the provision similarly.91 The amendment passed by a vote of 99 to 1.92

Section 1031 of the Senate bill became the conference report's Section 1021. It passed Congress and was signed by President Obama on December 31, 2011. President Obama issued a signing statement that reiterated his position that Section 1021 "breaks no new ground and is unnecessary."93 He cited Sections 1021(d) and (e) as "critical limitations" that "make clear beyond doubt that the legislation does nothing more than confirm authorities that the Federal courts have recognized as lawful under the 2001 AUMF."94 He stated also that his administration "will not authorize the indefinite military detention without trial of American citizens" and "will interpret section 1021 in a manner that ensures that any detention it authorizes complies with the Constitution, the laws of war, and all other applicable law."95

E. Proceedings Below

Plaintiff Christopher Hedges filed the initial complaint in this case on January 13, 2012, alleging that Section 1021 violated, inter alia, the First and Fifth Amendments and seeking declaratory and injunctive relief.96 On February 27, 2012, he filed a verified amended complaint, which added a number of plaintiffs,97 and moved for a temporary restraining order against enforcement of Section 1021, a motion that later was converted to a motion for a preliminary injunction.98 Plaintiffs submitted a number of affidavits in support of their motion, and the district court held an evidentiary hearing on March 30, 2012.99

Four plaintiffs submitted evidence that was considered by the district court and that is relevant to this appeal: two American citizens, Hedges and Alexa O'Brien,100 and two non-citizens, Birgitta Jonsdottir and Kai Wargalla.101 They are journalists or members of advocacy organizations who assert that they fear that their work makes them subject to indefinite detention under Section 1021.102 The government submitted no evidence.

The district court granted the preliminary injunction by opinion filed May 16, 2012.103 It concluded that each plaintiff had an actual fear of detention under Section 1021 and that this fear was reasonable.104 In reaching this latter conclusion, the court relied in significant part on the government's initial refusal to represent that the plaintiffs' activities would not subject them to detention under Section 1021. It rejected the government's contention that Section 1021 was just an "affirmation" of the AUMF that did nothing new.105 Determining further that the expressive conduct of each plaintiff had been chilled and that each had incurred concrete costs as a reasonable consequence of this fear, the court concluded that each plaintiff had standing to challenge Section 1021.106 It held that plaintiffs had shown a likelihood of success on claims that Section 1021 violated the First Amendment and was impermissibly vague in violation of the Fifth Amendment.107 Finally, it concluded that the other relevant factors supported preliminary injunctive relief.108

The government moved for reconsideration on May 25, 2012, clarifying its position by stating that, "[a]s a matter of law, individuals who engage in the independent journalistic activities or independent public advocacy described in plaintiffs' affidavits and testimony, without more, are not subject to law of war detention as affirmed by section 1021(a)-(c), solely on the basis of such independent journalistic activities or independent public advocacy."109 By agreement of the parties, the court proceeded directly to permanent injunction proceedings (thus mooting the motion for reconsideration) and took no new evidence for purposes of the permanent injunction.

Concluding that the government's "newly espoused position" did not alter its previous conclusion as to plaintiffs' standing,110 the court, on September 12, 2012, "permanently enjoin[ed] enforcement of § 1021(b)(2) in any manner, as to any person," generally affirming but also significantly expanding its prior analysis.111 It further held that "[m]ilitary detention based on allegations of `substantially supporting' or `directly supporting' the Taliban, al-Qaeda, or associated forces, is not encompassed within the AUMF and is enjoined by this Order regarding § 1021(b)(2)."112

This appeal followed.113 We granted a temporary stay of the district court's order on September 17, 2012, and then granted a stay pending appeal on October 2, 2012.

II. Discussion

The parties raise a number of important and difficult questions, but we need not reach most of them. We consider here only plaintiffs' standing under Article III of the Constitution. We begin with a brief discussion of the basic principles of Article III standing. We proceed to the proper construction of Section 1021 in relation to the AUMF. After clarifying what Congress did and did not do in passing Section 1021, we consider plaintiffs' standing given the record in this case. In that regard, we address first the American citizens, Hedges and O'Brien, and then the non-citizens, Jonsdottir and Wargalla.

A. General Principles of Standing

The judicial power of the United States, and thus the jurisdiction of federal courts, is limited by Article III of the Constitution to "Cases and Controversies."114 One aspect of this limitation is the requirement that the plaintiff have standing to sue, which "serves to prevent the judicial process from being used to usurp the powers of the political branches."115 "The party invoking federal jurisdiction bears the burden of establishing standing."116 The "`irreducible constitutional minimum'" requires that (1) the plaintiff "`have suffered an injury in fact — an invasion of a legally protected interest which is (a) concrete and particularized and (b) actual or imminent, not conjectural or hypothetical,'" (2) the injury be "`fairly traceable to the challenged action of the defendant,'" and (3) it "`be likely, as opposed to merely speculative, that the injury will be redressed by a favorable decision.'"117 Actual injury-in-fact exists when a defendant's actions have inflicted a concrete, present harm on the plaintiff. But the Supreme Court has recognized that a plaintiff in some circumstances may have standing to sue even when the plaintiff shows only an imminent threat of future harm or a present harm incurred in consequence of such a threat.118 We discuss these criteria in more detail as needed below.

B. The Proper Construction of Section 1021

We deal first with the meaning of Section 1021.

"As with any question of statutory interpretation, we begin by examining the text of the statute."119 In doing so, "we consider not only the bare meaning of the critical word or phrase but also its placement and purpose in the statutory scheme."120 It is "one of the most basic interpretive canons[ ] that a statute should be construed so that effect is given to all its provisions, so that no part will be inoperative or superfluous, void or insignificant."121 But "in interpreting a statute a court should always turn first to one, cardinal canon before all others," namely that "courts must presume that a legislature says in a statute what it means and means in a statute what it says there. When the words of a statute are unambiguous, then, this first canon is also the last: judicial inquiry is complete."122

The AUMF authorized the President to "use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons."123 Section 1021(a) "affirms" that the AUMF authority includes the detention of a "covered person[ ]," which under Section 1021(b) means (1) a "person who planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored those responsible for those attacks" or (2) a "person who was a part of or substantially supported al-Qaeda, the Taliban, or associated forces that are engaged in hostilities against the United States or its coalition partners, including any person who has committed a belligerent act or has directly supported such hostilities in aid of such enemy forces."

At first blush, Section 1021 may seem curious, if not contradictory. While Section 1021(b)(1) mimics language in the AUMF, Section 1021(b)(2) adds language absent from the AUMF. Yet Section 1021(a) states that it only "affirms" authority included under the AUMF, and Section 1021(d) indicates that Section 1021 is not "intended to limit or expand the authority of the President or the scope of the [AUMF]."

Fortunately, this apparent contradiction — that Section 1021 merely affirms AUMF authority even while it adds language not used in the AUMF — is readily resolved. It is true that the language regarding persons who "planned, authorized, committed, or aided" the 9/11 attacks (or harbored those who did) is identical in the AUMF and Section 1021(b)(1). The AUMF, however, does not merely define persons who may be detained, as does Section 1021(b). Instead, it provides the President authority to use "force" against the "nations, organizations, or persons" responsible for 9/11.124 Section 1021(b)(1) (read with Section 1021(a)) affirms that the AUMF authority to use force against the persons responsible for 9/11 includes a power to detain such persons. But it does not speak to what additional detention authority, if any, is included in the President's separate AUMF authority to use force against the organizations responsible for 9/11.

This is where Section 1021(b)(2), a provision concerned with the organizations responsible for 9/11 — al-Qaeda and the Taliban — plays a role.125 Section 1021(b)(2) naturally is understood to affirm that the general AUMF authority to use force against these organizations includes the more specific authority to detain those who were part of, or those who substantially supported, these organizations or associated forces.126 Because one obviously cannot "detain" an organization, one must explain how the authority to use force against an organization translates into detention authority.127 Hence, it is not surprising that Section 1021(b)(2) contains language that does not appear in the AUMF, notwithstanding Section 1021(d). Plaintiffs create a false dilemma when they suggest that either Section 1021 expands the AUMF detention authority or it serves no purpose.

Indeed, there are perfectly sensible and legitimate reasons for Congress to have affirmed the nature of AUMF authority in this way. To the extent that reasonable minds might have differed — and in fact very much did differ — over whether the administration could detain those who were part of or substantially supported al-Qaeda, the Taliban, and associated forces under the AUMF authority to use force against the "organizations" responsible for 9/11,128 Section 1021(b)(2) eliminates any confusion on that particular point. At the same time, Section 1021(d) ensures that Congress' clarification may not properly be read to suggest that the President did not have this authority previously — a suggestion that might have called into question prior detentions. This does not necessarily make the section a "`legislative attempt at an ex post facto "fix" ... to try to ratify past detentions which may have occurred under an overly-broad interpretation of the AUMF,'" as plaintiffs contend.129 Rather, it is simply the 112th Congress' express resolution of a previously debated question about the scope of AUMF authority.130

It remains to consider what effect Section 1021(e) has on this understanding. That provision states that "[n]othing in this section shall be construed to affect existing law or authorities relating to the detention of United States citizens, lawful resident aliens of the United States, or any other persons who are captured or arrested in the United States." Although this provision may appear superficially similar to Section 1021(d), nuances in the text and the legislative history make clear that Section 1021(e) actually is a significantly different provision.

As discussed above, in stating that Section 1021 is not intended to limit or expand the scope of the detention authority under the AUMF, Section 1021(d) mostly made a statement about the original AUMF — that is, it indicated that the specific power to detain those who were part of or who substantially supported the enumerated forces had been implicit in the more generally phrased AUMF.131 By contrast, in saying that Section 1021 shall not be construed to affect "existing law or authorities" relating to citizens, lawful resident aliens, or any other persons captured or arrested in the United States, Section 1021(e) expressly disclaims any statement about existing authority. Rather, it states only a limitation about how Section 1021 may be construed to affect that existing authority, whatever that existing authority may be.132

This understanding is reinforced by the legislative history. As discussed above, Senator Feinstein and others feared that Section 1021 would greatly expand the power of the government with particular reference to the authority to detain American citizens captured domestically. Senator Feinstein explained that she did not believe the government had such authority while Senators Graham and Levin, perhaps among others, believed that the government already did. Thus, Section 1021(e) was introduced specifically to effect a "truce" that ensured that — as to those covered by Section 1021(e) — courts would decide detention authority based not on Section 1021(b), but on what the law previously had provided in the absence of that enactment. This is not to say that Section 1021(e) specifically "exempts" these individuals from the President's AUMF detention authority, in the sense that Section 1022 expressly exempts United States citizens from its requirements.133 Rather, Section 1021(e) provides that Section 1021 just does not speak — one way or the other — to the government's authority to detain citizens, lawful resident aliens, or any other persons captured or arrested in the United States.134

We thus conclude, consistent with the text and buttressed in part by the legislative history, that Section 1021 means this: With respect to individuals who are not citizens, are not lawful resident aliens, and are not captured or arrested within the United States, the President's AUMF authority includes the authority to detain those responsible for 9/11 as well as those who were a part of, or substantially supported, al-Qaeda, the Taliban, or associated forces that are engaged in hostilities against the United States or its coalition partners — a detention authority that Section 1021 concludes was granted by the original AUMF. But with respect to citizens, lawful resident aliens, or individuals captured or arrested in the United States, Section 1021 simply says nothing at all.135

We recognize that Section 1021 perhaps could have been drafted in a way that would have made this clearer and that the absence of any reference to American citizens in Section 1021(b) led the district court astray in this case.136 Perhaps the last-minute inclusion of Section 1021(e) as an amendment introduced on the floor of the Senate explains the somewhat awkward construction. But that is neither here nor there. It is only our construction, just described, that properly gives effect to the text of all of the parts of Section 1021 and thus reflects congressional intent.137

C. American Citizen Plaintiffs

With this understanding of Section 1021, we may dispose of the claims of the citizen plaintiffs, Hedges and O'Brien. As discussed above, Section 1021 says nothing at all about the authority of the government to detain citizens. There simply is no threat whatsoever that they could be detained pursuant to that section.138 While it is true that Section 1021(e) does not foreclose the possibility that previously "existing law" may permit the detention of American citizens in some circumstances — a possibility that Hamdi clearly envisioned in any event — Section 1021 cannot itself be challenged as unconstitutional by citizens on the grounds advanced by plaintiffs because as to them it neither adds to nor subtracts from whatever authority would have existed in its absence. For similar reasons, plaintiffs cannot show that any detention Hedges and O'Brien may fear would be redressable by the relief they seek, an injunction of Section 1021.

Plaintiffs appear to contend that, even if Section 1021 is not applicable to Hedges and O'Brien, the wording of Section 1021(e) seems to "assume" that citizens may be detained if they have substantially supported al-Qaeda and that Hedges and O'Brien therefore have standing to challenge it. We disagree. There is nothing in Section 1021 that makes any assumptions about the government's authority to detain citizens under the AUMF. Rather, Section 1021(e) quite specifically makes clear that the section should not be construed to affect in any way existing law or authorities relating to citizen detention, whatever those authorities may provide.

D. Non-citizen Plaintiffs

The claims of Jonsdottir and Wargalla stand differently. Whereas Section 1021 says nothing about the government's authority to detain citizens, it does have real meaning regarding the authority to detain individuals who are not citizens or lawful resident aliens and are apprehended abroad.139 It provides that such individuals may be detained until the end of hostilities if they were part of or substantially supported al-Qaeda, the Taliban, or associated forces. To be sure, Section 1021 in substance provides also that this authority was implicit in the original AUMF. But, as discussed above, that the 112th Congress in passing Section 1021 expressed such a view does not mean that Section 1021 itself is a nullity. It is not immediately apparent on the face of the AUMF alone that the President had the authority to detain those who substantially supported al-Qaeda, and indeed many federal judges had concluded otherwise prior to Section 1021's passage. Hence, Section 1021(b)(2) sets forth an interpretation of the AUMF that had not previously been codified by Congress. Where a statute codifies an interpretation of an earlier law that is subject to reasonable dispute, the interpretive statute itself may affect the rights of persons under the earlier law.

As the standing inquiry as to these two plaintiffs is more involved, we discuss the relevant facts and applicable law in detail.140

1. Relevant Facts

Jonsdottir is a citizen of Iceland and a member of its parliament. She is an activist and spokesperson for a number of groups, including WikiLeaks, an organization famous for releasing troves of classified information of the United States government to the public. In early 2010, Jonsdottir helped WikiLeaks produce the video Collateral Murder, which allegedly depicts an American helicopter opening fire on unarmed individuals in Iraq. She testified that, around the same time, she had been working with people around the world, including some at WikiLeaks, to create a safe haven for freedom of information in Iceland. Jonsdottir testified that Collateral Murder made WikiLeaks known to the world shortly before its release later in 2010 of the Afghan and Iraq war logs and a substantial number of State Department cables — classified information allegedly leaked to WikiLeaks by one Bradley Manning. Jonsdottir further testified that she is aware that Manning has been charged by the United States government for aiding the enemy on the ground that he knew the classified information he provided to WikiLeaks would end up in the hands of al-Qaeda. She testified that a number of American politicians have called WikiLeaks a terrorist organization and that the government has been considering criminal charges against the organization and its founder, Julian Assange. As part of this investigation, she has received a subpoena from a federal grand jury for content from her Twitter account. She has received a number of invitations to speak in the United States, but will not travel here — thereby forgoing contacts and compensation — because of the subpoena and her fears of detention under Section 1021.

Wargalla, a German citizen, is an organizer and activist based in London, and is associated with the organizations Revolution Truth, Occupy London, and Justice for Assange UK. She testified that Occupy London has been listed as a terrorist group by the City of London police department. Moreover, she testified that she has been a supporter of WikiLeaks since 2010 as it was releasing the classified information noted above. Since January 2011, she has organized rallies, demonstrations, and protests on behalf of Assange and Manning. She testified that she has met Assange, who is familiar with her support, and has had contact with other employees of WikiLeaks. Wargalla testified that her fears of detention under Section 1021 have made it nearly impossible to pursue her everyday work.

The district court found that both Jonsdottir and Wargalla had an actual fear of detention under Section 1021 and had incurred costs and other present injuries due to this fear.141

2. Fear-based Standing Law

We have no occasion to disturb the factual findings of the district court, which are well-supported by the record, or to question the truth of the factual testimony of the plaintiffs, which the district court found credible.142 Rather, we are faced only with a question of law: whether the non-citizen plaintiffs' fears of enforcement, as well as any present costs they have incurred as a result of those fears, establish their standing to bring this challenge.

As discussed earlier, the Supreme Court has recognized that such fears may support standing when the threat creating the fear is sufficiently imminent. The Supreme Court's jurisprudence regarding how imminent a threat must be in order to support standing, however, has been less than clear. In Clapper v. Amnesty International USA,143 the Court recently concluded that the plaintiffs did not have standing to challenge a statute expanding the government's surveillance capabilities as violating, inter alia, the First and Fourth Amendments because they had failed to show that government interceptions of their communications were "certainly impending."144 The Court further concluded that, to the extent the plaintiffs had suffered present injuries because of their fear of such interception, they "cannot manufacture standing by choosing to make expenditures based on hypothetical future harm that is not certainly impending."145 Yet at the same time, a footnote in Clapper recognized that the Court has not uniformly required that it be "literally certain that the harms [plaintiffs] identify will come about" and sometimes found standing to sue where plaintiffs showed only a "`substantial risk' that the harm will occur, which may prompt plaintiffs to reasonably incur costs to mitigate or avoid that harm."146 The Court did not explain when such a standard might apply, noting only that the plaintiffs in Clapper failed that test as well to whatever extent it might have been relevant and distinct.147

One of the cases that Clapper cited as using a potentially more permissive standard was a preenforcement challenge to a criminal statute.148 In Babbitt v. United Farm Workers National Union,149 the Court held that when a plaintiff "has alleged an intention to engage in a course of conduct arguably affected with a constitutional interest, but proscribed by a statute, and there exists a credible threat of prosecution thereunder, he should not be required to await and undergo a criminal prosecution as the sole means of seeking relief."150 Put differently, the Court held that a plaintiff has standing to make a preenforcement challenge "when fear of criminal prosecution under an allegedly unconstitutional statute is not imaginary or wholly speculative."151 It has applied that principle in a number of cases challenging criminal statutes — finding standing where the plaintiff "will have to take significant and costly compliance measures or risk criminal prosecution"152 — and in the civil context as well.153 The First Circuit has observed that the Babbitt standard sets a "low threshold" and is "quite forgiving" to plaintiffs seeking such preenforcement review.154

Part of what makes the Court's approach in these cases "forgiving" is that it appears willing to presume that the government will enforce the law as long as the relevant statute is "recent and not moribund."155 Thus, in numerous preenforcement cases where the Supreme Court has found standing on a showing that a statute indisputably proscribed the conduct at issue, it did not place the burden on the plaintiff to show an intent by the government to enforce the law against it. Rather, it presumed such intent in the absence of a disavowal by the government or another reason to conclude that no such intent existed.156

These cases do not explain how to evaluate preenforcement standing when it is not apparent whether a plaintiff is subject to the statute and when the government actively disputes that it is. Nor do they address a situation in which the government disavowed any intention to prosecute plaintiff, regardless of the appropriate interpretation of the statute.157 But this Court did consider such circumstances in Vermont Right to Life Committee v. Sorrell.158

The state there argued that the plaintiff lacked standing because the statute did not proscribe plaintiff's conduct. A divided panel of this Court rejected that argument in reliance on Babbitt. The majority concluded that "while there may be other, perhaps even better, definitions" of the disputed statutory term, plaintiff's interpretation of the statute, which would have covered its conduct, was "reasonable enough that [plaintiff] may legitimately fear that it will face enforcement of the statute by the [s]tate brandishing the definition proffered" by plaintiff.159 To the extent that the state contended that it had no intention of suing plaintiff for its activities, we said "there is nothing that prevents the [s]tate from changing its mind" and that allowing the state's presently stated intention to defeat standing "would be placing [plaintiff's] asserted First Amendment rights at the sufferance of Vermont's Attorney General."160

Similarly, in Pacific Capital Bank v. Connecticut,161 we relied on Vermont Right to Life to hold that plaintiff established standing to challenge a civil penalty provision despite the state's argument that it never had enforced the statute against anyone and that "it is unknown how the [s]tate will apply that section in any future enforcement action."162

3. Coverage Under Section 1021(b)(2)

As in Vermont Right to Life, the government here disputes that plaintiffs are subject to the statute. Plaintiffs never articulate a precise theory on which they fear detention under Section 1021(b)(2) — that is, in what sense the government may conclude that they were a "part of or substantially supported al-Qaeda, the Taliban, or associated forces that are engaged in hostilities against the United States or its coalition partners." The strongest argument would seem to be a contention that the work of Jonsdottir and Wargalla substantially, if indirectly, supports al-Qaeda and the Taliban as the term "support" is understood colloquially.163 The record demonstrates a number of ways in which the government has concluded, or would have a basis to conclude, that WikiLeaks has provided some support to al-Qaeda and the Taliban. This includes the evidence that the government is prosecuting Manning for aiding the enemy by his releases to WikiLeaks and news articles in the record or cited by the Jonsdottir declaration reporting on the immense amount of classified information that WikiLeaks made public, much of which is related specifically to the government's military efforts against al-Qaeda and the Taliban.164 One perhaps might fear that Jonsdottir's and Wargalla's efforts on behalf of Wiki-Leaks could be construed as making them indirect supporters of al-Qaeda and the Taliban as well.

The government rejoins that the term "substantial support" cannot be construed so in this particular context. Rather, it contends that the term must be understood — and limited — by reference to who would be detainable in analogous circumstances under the laws of war. It points to (1) the Hamdi plurality's limitation of the duration of the detention authority it recognized based on the laws of war, (2) the March 2009 Memo's repeated invocation of law-of-war limiting principles and the legislative history suggesting that Section 1021 was meant to codify the interpretation that the Memo set forth, (3) Section 1021(d), to the extent that Hamdi and the administration suggested that the laws of war inform AUMF authority, as bearing on how broadly "substantial support" may be construed, and (4) the references to "law of war" in Section 1021 itself, albeit not in Section 1021(b)(2). The government then contends that individuals like Jonsdottir and Wargalla are civilians who are not detainable under these law-of-war principles and so cannot reasonably fear detention under Section 1021.

In these circumstances, we are faced with a somewhat peculiar situation. The government has invited us to resolve standing in this case by codifying, as a matter of law, the meaningful limits it has placed on itself in its interpretation of Section 1021. We decline the government's invitation to do so. Thus, we express no view regarding whether the laws of war inform and limit detention authority under Section 1021(b)(2) or whether such principles would foreclose the detention of individuals like Jonsdottir and Wargalla. This issue presents important questions about the scope of the government's detention authority under the AUMF, and we are wary of allowing a preenforcement standing inquiry to become the vehicle by which a court addresses these matters unless it is necessary. Because we conclude that standing is absent in any event, we will assume without deciding that Section 1021(b)(2) covers Jonsdottir and Wargalla in light of their stated activities.165

4. Threat of Enforcement

We next consider whether there is a sufficient threat of enforcement even given this assumption. This inquiry corresponds to (1) our suggestions in Vermont Right to Life and Pacific Capital Bank that a plaintiff has standing when it "`may legitimately fear that it will face enforcement'" under its reasonable interpretation of the statute166 and (2) the Supreme Court's recognition that a preenforcement challenge is justiciable when enforcement is a "realistic danger,"167 when there is a "credible threat of prosecution,"168 or when a plaintiff has an "actual and well-founded fear"169 of such enforcement. As noted above, however, neither this Court nor the Supreme Court has required much to establish this final step in challenges to ordinary criminal or civil punitive statutes. Rather, we have presumed that the government will enforce the law.

The question is the extent to which such a presumption is applicable here. The district court concluded that it was, reasoning that Section 1021 "is equivalent to a criminal statute" because "the possibility of being placed in indefinite military detention is the equivalent of a criminal penalty."170 Certainly we agree that military detention until the termination of hostilities would be severe and that the prospect of such detention can be "as inhibiting of speech as can trepidation in the face of threatened criminal prosecution."171 But that is a separate question from whether it is appropriate to presume that Section 1021 will be enforced as would any criminal or civil punitive statute.

On this point, there are several important differences between Section 1021 and a typical statute imposing criminal or civil penalties. Section 1021 is not a law enforcement statute, but an affirmation of the President's military authority.172 As discussed above, it applies only to individuals who are not citizens, are not lawful resident aliens, and are apprehended outside the United States. It thus speaks entirely to the authority of the President in the context of military force, national security, and foreign affairs, areas in which the President generally enjoys "unique responsibility"173 and "broad discretion."174 The Supreme Court has recognized that "Congress cannot anticipate and legislate with regard to every possible action the President may find it necessary to take" in the fields of national security and foreign affairs.175 As a result, "Congress — in giving the Executive authority over matters of foreign affairs — must of necessity paint with a brush broader than that it customarily wields in domestic areas."176

Moreover, Section 1021 "at most authorizes — but does not mandate or direct" — the detention that plaintiffs fear.177 To be sure, the executive branch enjoys prosecutorial discretion with regard to traditional punitive statutes. Congress generally does not mandate or direct criminal prosecution or civil enforcement.178 But we can distinguish between Congress, on the one hand, proscribing a certain act and then leaving it to the President to enforce the law under his constitutional duty to "take Care that the Laws be faithfully executed"179 and Congress, on the other hand, authorizing the President to use a certain kind of military force against non-citizens abroad.

Consequently, there is a world of difference between assuming that a state executive will enforce a statute imposing civil penalties for certain campaign finance violations180 — or even that the executive branch will enforce a federal criminal statute barring provision of material support to terrorists181 — and assuming that the President will detain any non-citizen abroad that Congress authorizes him to detain under the AUMF. Clapper further supports this understanding, as it made clear that plaintiffs cannot establish standing on the basis of speculation about how the government may choose to utilize its authority to engage in foreign surveillance.182 In short, while it generally may be appropriate to presume for standing purposes that the government will enforce the law against a plaintiff covered by a traditional punitive statute, such a presumption carries less force with regard to a statute concerned entirely with the President's authority to use military force against non-citizens abroad.183 Thus, in the circumstances of this case, Jonsdottir and Wargalla must show more than that the statute covers their conduct to establish preenforcement standing.

We need not quantify precisely what more is required184 because Jonsdottir and Wargalla have shown nothing further here. Indeed, they have not established a basis for concluding that enforcement against them is even remotely likely. We reach this conclusion independent of the government's litigation position on appeal that plaintiffs are "in no danger whatsoever" of being detained on the basis of their stated activities.185

First, even assuming that Jonsdottir and Wargalla fall within the ambit of authority provided by the statute, this is certainly not a case in which "the law is aimed directly at plaintiffs."186 They point to nothing in the record, or in the text or legislative history of Section 1021, that suggests that the statute was passed to facilitate the military detention of individuals specifically like them.

Second, while we do not hold that a specific threat of enforcement is necessary, neither Jonsdottir nor Wargalla has adduced any evidence that the government intends or has threatened to place them in military detention.187

Third, they have not put forth evidence that individuals even remotely similarly situated have been subjected to military detention.188 The government argues that this latter failure is particularly meaningful because, it contends, Section 1021 codified an interpretation "that the President had long articulated and exercised and that the Judiciary had repeatedly recognized."189

To be sure, the government overstates its case on this point. As the history of litigation regarding the scope of AUMF detention authority shows, numerous courts criticized or rejected the government's reliance on substantial support in the March 2009 Memo. Prior to that, a divided Fourth Circuit set forth a number of different interpretations of executive detention authority, none of which resembled the government's position.190 While the D.C. Circuit's decision in Al-Bihani is supportive of the government's standard, it focused primarily on a "purposeful and material support" standard, the relationship of which to "substantial support" is not clear. Simply put, to the extent that Congress resolved a previously debated question about the scope of AUMF detention authority in passing Section 1021, it was not obvious that the answer it provided is the one that ultimately would have prevailed had Congress not passed anything at all.191 In light of this uncertainty, at least in principle Section 1021's codification of the "substantial support" standard could place the administration on stronger footing to detain individuals under such a theory than it might have been willing to risk previously.

Nevertheless, plaintiffs bear the burden of establishing standing.192 Whether Section 1021 can or will alter executive practice, particularly with regard to individuals like them, is purely a matter of speculation. The fact remains that — despite the executive at least nominally asserting the authority to detain on the basis of "support" since the 2004 CSRT enemy combatant definition, and on the basis of "substantial support" since the March 2009 Memo,193 and despite the D.C. Circuit recognizing the lawfulness of detention at least on the basis of "purposeful and material support" since 2010 — plaintiffs have provided no basis for believing that the government will place Jonsdottir and Wargalla in military detention for their supposed substantial support. In all the circumstances, plaintiffs have not shown a sufficient threat of enforcement to establish standing. Moreover, they cannot "manufacture standing" based on any present injuries incurred due to their expressed fears.194

Nothing in this decision should be confused as deference to the political branches because the case involves national security and foreign affairs. We adhere to the principle that courts have a vigorous and meaningful role to play in assessing the propriety of military detention, as the Supreme Court has made clear in cases from Hamdi to Boumediene.195 We hold only that a court first must satisfy itself that the case comports with the "irreducible constitutional minimum" of Article III standing.196 This inquiry is rooted in fundamental separation-of-powers principles and must be "especially rigorous" where, as here, the merits of the dispute require the court to "decide whether an action taken by one of the other two branches of the Federal Government was unconstitutional."197 Section 1021 is concerned entirely with the military authority of the President with respect to non-citizens abroad — a context in which Congress provides the President broad authority to exercise with considerable discretion. Particularly after Clapper, plaintiffs must show more than that they fall within the ambit of this authority to establish the sufficient threat of enforcement necessary for Article III standing. They have failed to do so here.

A final note: Plaintiffs repeatedly refer to the First Amendment overbreadth doctrine as if it were relevant to whether they have established Article III standing. It is not. Relaxing the general prudential rule against third-party standing, the overbreadth doctrine permits a plaintiff to represent the legal interests of parties not before the court when seeking facial invalidation of a statute under the First Amendment, if certain conditions are met.198 Critically, "[w]e allow a party to bring an overbreadth challenge where that party `satisfies the Article III requirement of "injury-in-fact" and where it can be expected satisfactorily to frame the issues in the case.'"199 In other words, the overbreadth doctrine speaks to whose interests a plaintiff suffering Article III injury may represent. It does not provide a reason to find such injury where none is present or imminently threatened in the first instance.

III. Conclusion

In sum, Hedges and O'Brien do not have Article III standing to challenge the statute because Section 1021 simply says nothing about the government's authority to detain citizens. While Section 1021 does have meaningful effect regarding the authority to detain individuals who are not citizens or lawful resident aliens and are apprehended abroad, Jonsdottir and Wargalla have not established standing on this record. We VACATE the permanent injunction and REMAND for further proceedings consistent with this opinion.