In precedent stretching back to the Chinese Exclusion Case of 1889, the Supreme Court has held that Congress possesses "plenary power" to regulate immigration. This power, according to the Court, is the most complete that Congress possesses. It allows Congress to make laws concerning aliens that would be unconstitutional if applied to citizens. And while the immigration power has proven less than absolute when directed at aliens already physically present within the United States, the Supreme Court has interpreted the power to apply with most force to the admission and exclusion of nonresident aliens abroad. The Court has upheld or shown approval of laws excluding aliens on the basis of ethnicity, gender and legitimacy, and political belief. Outside of the immigration context, in contrast, laws that discriminate on such bases are almost always struck down as unconstitutional. To date, the only established limitation on Congress's power to exclude aliens concerns lawful permanent residents (LPRs): they, unlike nonresident aliens, generally cannot be denied entry without a fair hearing as to their admissibility. The plenary power doctrine has long drawn scholarly criticism. Some legal commentators contend that the doctrine lacks a coherent rationale, and that it is an anachronism belonging to an earlier era of constitutional law predating the development of modern individual rights jurisprudence. More than 125 years after its initial recognition of the plenary power doctrine, however, the Supreme Court has continued to rely on it in immigration cases. Some commentators have argued that the Court is in the process of narrowing the parameters of the doctrine's applicability, although they find support for this argument mainly in cases outside of the exclusion context. The Constitution does not mention immigration. It does not expressly confer upon any of the three branches of government the power to control how citizens of other countries enter, live, and remain in the United States. Parts of the Constitution address related subjects. The Supreme Court has sometimes relied upon Congress's enumerated powers over naturalization and foreign commerce, and to a lesser extent upon the Executive's implied Article II foreign affairs power, as sources of federal immigration power. Significantly, however, the Court has also consistently attributed the immigration power to the federal government's inherent sovereign authority to control its borders and its relations with foreign nations. This inherent sovereign power, according to the Court, gives Congress essentially unfettered authority to restrict the entry of nonresident aliens. The Court has determined that the executive branch, by extension, possesses unusually broad authority to enforce laws pertaining to alien entry, and to do so under a level of judicial review much more limited than that which would apply outside of the exclusion context. The scope of the federal government's power to exclude aliens is at the forefront of litigation concerning two successive executive orders (the second revising and replacing the first) issued by President Donald Trump that, in their revised form, seek to deny entry temporarily to foreign nationals from six predominantly Muslim countries and to all refugees, subject to limited waiver. A series of lower court decisions largely enjoined implementation of the orders. In particular, courts ruled that the President's travel restrictions are likely unconstitutional or exceed his statutory authority. The Supreme Court granted certiorari to review decisions by the U.S. Courts of Appeals for the Fourth and Ninth Circuits that upheld nationwide injunctions against the revised executive order. The Supreme Court also partially stayed the injunctions, allowing the executive branch to implement the revised order in part pending the outcome of the litigation. A decision by the Court on the merits of these cases, which have come to be known as the "Travel Ban" litigation, could deliver a major statement about the constitutional and statutory scope of the President's power to exclude aliens. The litigation has threshold issues, however, such as questions of mootness and standing, that may well prevent the Court from reaching the merits, particularly following the issuance of a presidential proclamation superseding and somewhat modifying some of the entry restrictions at issue in the case. This report provides an overview of the legislative and executive powers to exclude aliens. First, the report discusses a gatekeeping legal principle that frames those powers: nonresident aliens outside the United States cannot challenge their exclusion from the country. Second, the report analyzes the extent to which the constitutional and statutory rights of U.S. citizens limit the exclusion power under the "facially legitimate and bona fide" test of Kleindienst v. Mandel . The report concludes with a case study. The report applies the principles of the Supreme Court's immigration jurisprudence to the two primary claims that U.S. persons and entities have pressed against the President's revised executive order in the "Travel Ban" litigation: (1) that the revised order violates the Establishment Clause; and (2) that the revised order violates the Immigration and Nationality Act (INA). As discussed later in the report, case law on the exclusion of aliens has come to focus upon whether the rights of U.S. citizens limit the government's power to exclude. The case law arrived at this issue, however, only after the Supreme Court had worked out an essential underlying principle: nonresident aliens outside the United States have no constitutional or statutory rights with respect to entry and therefore no legal grounds to challenge their exclusion. The Supreme Court developed this principle in a series of cases between the late 19 th and mid-20 th centuries about aliens denied admission after arriving by sea. The law at the time allowed such aliens to challenge the legality of their exclusion by filing a petition for habeas corpus in federal district court. This procedural right, however, proved hollow. In every case, the Supreme Court determined that the federal government's sovereign prerogative to forbid the entry of foreigners foreclosed the aliens' claims. In one famous case, the Court declared itself powerless to review the government's decision to exclude—without any explanation other than that the entry would be "prejudicial"—the German bride of a U.S. World War Two veteran. In another case, the Court refused to question the government's undisclosed reasons for denying entry to an essentially stateless alien returning to the United States after a prior period of residence, even though the exclusion relegated the stateless alien to indefinite detention on Ellis Island. The Supreme Court has since relied upon these cases for the proposition that excluded nonresident aliens cannot state legal claims with respect to entry. The related doctrine of consular nonreviewability precludes judicial review of visa denials. This doctrine developed in the lower courts and appears to derive from the line of Supreme Court cases described above. The consular nonreviewability doctrine, like the rule foreclosing alien claims itself, does not have a clearly enunciated theoretical foundation. It does have a clear consequence, however: the millions of nonresident aliens denied visas each year at U.S. consulates abroad cannot themselves challenge the visa denial in federal court. The Supreme Court has never endorsed the doctrine by name, but the Court has twice stated (without holding) that nonresident aliens cannot challenge visa denials. Put simply, under the consular nonreviewability doctrine and the related Supreme Court cases, nonresident aliens located outside the United States cannot challenge their exclusion from the country in federal court. The rule against alien challenges to denials of entry becomes more convoluted in the context of arriving aliens denied entry at the border, notwithstanding the rule's provenance in cases about such aliens. Arriving alien cases, unlike visa cases, can involve people stranded at the nation's threshold and, accordingly, sometimes present issues that go beyond the denial of entry itself to implicate the government's treatment of persons under its control. Whether the Constitution protects arriving aliens from unduly burdensome enforcement measures, such as prolonged detention pending removal, remains a disputed question. But Congress has provided certain statutory protections in this regard. Moreover, arriving aliens have succeeded in obtaining judicial review of statutory claims against detention or interdiction at sea by U.S. authorities. Such review for aliens pressing claims against the denial of visas abroad, in contrast, does not exist. To be sure, the exclusion power with respect to arriving aliens remains vast, and Congress relied on this broad power in 1996 when it created expedited removal procedures for many arriving aliens that limit or foreclose judicial review. But the exclusion power applies with its maximum force, in practice if not in theory, only to aliens who apply to enter from abroad, because such applications isolate the issue of denial of entry from the treatment issues that physical presence at the border or inside the country sometimes triggers. It is this core of the exclusion power that the remainder of this report addresses and that the Travel Ban cases, which concern the exclusion of aliens generally located far from the nation's shores, implicate most directly. Even as applied to aliens abroad, the rule against nonresident alien challenges to denials of entry has a major limitation: the rule only forecloses challenges brought by nonresident aliens themselves. Thus, if a U.S. citizen claims that the exclusion of an alien violated the U.S. citizen ' s rights , the rule against alien challenges does not apply. Cases that invoke this limitation account for the entirety of the Supreme Court's modern exclusion jurisprudence. The Court has not considered a nonresident alien's own challenge to a denial of entry in decades. The question about the extent to which U.S. citizens can challenge an alien's exclusion, on the other hand, has occupied the Court in three important cases since 1972: Kleindienst v. Mandel , Fiallo v. Bell , and the splintered Kerry v. Din . Under the rule that these cases establish, the government need only articulate a "facially legitimate and bona fide" reason for excluding a nonresident alien or class of aliens in order to prevail against an American citizen's claim that his or her constitutional rights have been violated by the exclusion. This section of the report discusses the three exclusion cases, an understanding of each of which is fundamental to this area of the Supreme Court's jurisprudence. Next, the section discusses the cases' implications for the scope of congressional power to exclude aliens and the scope of the concomitant executive power. The section ends by noting two unresolved issues concerning the executive power: (1) the extent to which U.S. citizens may challenge an alien's exclusion on statutory grounds; and (2) the extent to which the Constitution limits the Executive's exclusion decisions under broad delegations of congressional power. In 1972, the Court confronted a case in which a group of American professors claimed that the exclusion of a Belgian intellectual, Ernest Mandel, violated the American professors'—and not Mandel's—First Amendment rights. The professors had invited Mandel to speak at their universities. A provision of the INA rendered him ineligible for a visa because of his communist political beliefs. A separate provision authorized the Attorney General to waive Mandel's ineligibility upon a recommendation from the Department of State, but the Attorney General declined to do so. The case produced the test that continues to govern claims that the exclusion of an alien violates an American citizen's constitutional rights: [P]lenary congressional power to make policies and rules for exclusion of aliens has long been firmly established.... We hold that when the Executive exercises [a delegation of this power] negatively on the basis of a facially legitimate and bona fide reason , the courts will neither look behind the exercise of that discretion, nor test it by balancing its justification against the First Amendment interests of those who seek personal communication with the applicant. Applying this test, the Court upheld Mandel's exclusion on the basis of the government's explanation that it denied the waiver because Mandel had abused visas in the past. The American professors and two dissenting Justices pointed to indications of pretext and argued that Mandel had actually been excluded because of his communist ideas. Nonetheless, the majority refused to "look behind" the government's justification to determine whether any evidence supported it. In other words, the Court accepted at face value the government's explanation for why it denied Mandel permission to enter. The "facially legitimate and bona fide" standard resolved what the Court saw as the major dilemma that the dispute over Mandel's visa posed for the bedrock principles of its immigration jurisprudence. The American professors, unlike Mandel himself or the unadmitted aliens from prior exclusion cases, stated a compelling First Amendment claim. But for the Court to grant relief on that claim, or even to grant full consideration of the claim, would have undermined Congress's plenary power to exclude aliens by interjecting the courts into the exclusion process. After all, nearly every exclusion for communist ideology would have been susceptible to the same attack. The "facially legitimate" standard protected the plenary power against dilution by limiting the reach of the American professors' claim. Under the standard, the professors were not entitled to balance their First Amendment rights against the government's exclusion power; they were entitled only to a constitutionally valid statement as to why the government exercised the exclusion power. Significantly, the Court left open the question whether the American professors' rights entitled them to even that much. Although the government proffered a "facially legitimate and bona fide" justification for Mandel's exclusion, the Court declined to say whether the government would have prevailed even if it had offered "no justification whatsoever." The Court has followed Mandel in two subsequent exclusion cases. These cases—one concerning a statute and one concerning the Executive's application of a statute—generally reinforce the notion of the government's plenary power to exclude aliens even in the face of constitutional challenges brought by U.S. citizens. The second case, however, includes limiting dicta that appears to contemplate a pathway for future challenges. First, in Fiallo v. Bell , the Court upheld a provision of the INA that classified people by gender and legitimacy. The statute granted special immigration preferences to the children and parents of U.S. citizens and LPRs, unless the parent-child relationship at issue was that of a father and his illegitimate child. Four U.S. citizens and permanent residents claimed that the restriction violated their equal protection rights by disqualifying their children or fathers from the preferences. Despite the "double-barreled discrimination" on the face of the statute, the Court upheld it as a valid exercise of Congress's "exceptionally broad power to determine which classes of aliens may lawfully enter the country." Although it relied on Mandel , the Fiallo Court did not identify a concrete "facially legitimate or bona fide" justification for the statute. Instead, the Court simply surmised that a desire to combat visa fraud or to emphasize close family ties may have motivated Congress to impose the gender and legitimacy restrictions. Similar to the analysis in Mandel , the Fiallo Court justified its limited review of the facially discriminatory statute as a way to prevent the assertion of U.S. citizen rights from undermining the sovereign prerogative to exclude aliens. In the second case, Kerry v. Din , the Court considered a U.S. citizen's claim that the Department of State (State) violated her due process rights by denying her husband's visa application without sufficient explanation. State indicated that it denied the visa under a terrorism-related ineligibility, but it did not disclose the factual basis of its decision. The Court rejected the claim by a vote of 5 to 4 and without a majority opinion. Justice Scalia, writing for a plurality of three Justices, did not reach the Mandel analysis because he concluded that Din did not have a protected liberty interest under the Due Process Clause in her husband's ability to immigrate. But Justice Kennedy, in a concurring opinion for himself and Justice Alito, rejected the claim under the "facially legitimate and bona fide reason" test after assuming without deciding that the visa denial did implicate due process rights. Justice Kennedy's concurring opinion made two significant statements about how Mandel works in application. First, the government satisfies the "facially legitimate and bona fide reason" standard by citing the statutory provision under which it has excluded the alien. According to Justice Kennedy, such a citation fulfills both the "facially legitimate" and "bona fide" prongs of the test. Thus, because the government stated that it denied Din's husband's visa application under the terrorism-related ineligibility, it provided an adequate justification even though it did not disclose the factual basis for applying the ineligibility. Pointing to the statute suffices. Second, however, Justice Kennedy inserted a caveat into his application of the "bona fide" prong: Absent an affirmative showing of bad faith on the part of the consular officer who denied Berashk [Din's husband] a visa—which Din has not plausibly alleged with sufficient particularity— Mandel instructs us not to "look behind" the Government's exclusion of Berashk for additional factual details beyond what its express reliance on [the terrorism-related ineligibility] encompassed. In other words, under Justice Kennedy's reading of the Mandel standard, courts will assume that the government has a valid basis for excluding an alien under a given statute unless an affirmative showing suggests otherwise. In Din , the facts did not suggest bad faith, because Din's own complaint revealed a connection between the statutory ineligibility and her husband's case. Justice Kennedy therefore had no occasion to apply the caveat, and the opinion does not clarify what kind of "affirmative showing" would trigger it. Nonetheless, as discussed later in the report, the mere mention of a bad faith exception arguably hedges, in a way that has proved significant in the Travel Ban cases, against the absolutism of Mandel 's instruction not to examine the government's underlying factual basis for excluding a given alien. Mandel and Din , in their examination of executive application of the immigration laws, appeared to take the absoluteness of Congress's exclusion power as a given. In Din , Justice Kennedy grounded his conclusion—that a visa denial withstands constitutional attack so long as the government ties the exclusion to a statutory provision—on the premise that Congress can impose whatever limitations it sees fit on alien entry. In other words, because Congress's limitations are valid per se , executive enforcement of those limitations is also valid. Mandel makes the same point, albeit mainly through omission. Recall that the case concerned application of an INA provision that rendered the Belgian academic ineligible for a visa because he held communist political beliefs. The Court acknowledged that the statute triggered First Amendment concerns by limiting, based on political belief, U.S. citizens' audience with foreign nationals. But the Court did not decide whether the statute violated the First Amendment. Rather, the Court simply accepted that Congress had the power to impose such an idea-based entry limitation. As a result, the Mandel decision considered only the First Amendment implications of the Attorney General's refusal to waive Mandel's communism-based ineligibility, not the statutory premise of the ineligibility. The untested assumption underlying Mandel and Din —that Congress's immigration power encompasses the power to exclude based on any criteria whatsoever, including political belief—raises a fundamental question about the nature of the plenary power. Often, the Court has described the power as one that triggers judicial deference , meaning that courts may conduct only a limited inquiry when considering the constitutionality of an exercise of the immigration power. But the plenary power doctrine, as some scholars have noted, can be understood another way, one that perhaps makes more sense of Mandel : the "plenary" refers to the scope of the power itself, in substance, and not to its immunity from judicial review. The congressional power to admit or exclude aliens is so complete, this theory goes, as to override the constitutional limitations that typically constrain legislative action. For example, the power overrides the First Amendment principles that would invalidate legislation that expressly provides for unfavorable treatment based on political belief in almost any other context. Aspects of Fiallo , however, arguably do not support this concept of a substantively limitless congressional power to regulate alien entry. Unlike Mandel and Din , which examined the Executive's application and implementation of authority delegated by statute, Fiallo squarely considered the constitutionality of a statute itself. And while Fiallo 's outcome (upholding an immigration law that discriminated by gender and legitimacy) aligns with the concept of an unbridled legislative power, the Court's reasoning wavered between statements suggesting that the legislative power might have limits and statements describing the power as absolute. The lack of clarity in the opinion seemed to stem from the awkwardness of applying Mandel —which fashioned a rule for review of executive action (the "facially legitimate and bona fide" test)—in a case reviewing legislative action. Ultimately, the Fiallo Court cited the Mandel test as an analogue but did not actually apply the test. Rather, the Court upheld the statute at issue under something that looked like a version of rational basis review, one in which a hypothetical justification suffices to sustain the statute. While extremely deferential, this version of rational basis review implies an underlying constitutional limitation against legislative unreasonableness, at least in theory. In other words, an even-handed reading of Fiallo suggests that statutes regulating the admission of aliens must at least be reasonable. Some scholars have argued that Fiallo was incorrectly decided and that stricter constitutional scrutiny should apply to admission and exclusion laws that classify aliens by factors such as race, religion, and gender. To date, this argument does not find support in Supreme Court precedent. To be sure, the Supreme Court has made clear that Congress cannot deny certain rights to aliens subject to criminal or deportation proceedings within the United States, and the federal government cannot deny some procedural protections to LPRs returning from brief trips from abroad. But the Court has never suggested that laws regulating the admission of nonresident aliens trigger anything more than the deferential rational basis review that it applied to the gender-based immigration preferences statute at issue in Fiallo . In other words, the Court has never called Fiallo into question. In one recent case, Sessions v. Morales-Santana , the Supreme Court applied heightened constitutional scrutiny to strike down a derivative citizenship statute that, much like the statute in Fiallo , used gender classifications. However, the Morales-Santana Court distinguished Fiallo and the plenary power doctrine by noting that the statute before it concerned citizenship, not immigration. Accordingly, Morales-Santana does not appear to portend imminent reconsideration of Fiallo . To summarize, dicta in the exclusion cases that decided challenges to executive action, Mandel and Din , give the impression of a substantively absolute congressional power to control the entry of aliens. But courts have generally interpreted Fiallo , which concerned a direct challenge to a law regulating alien admission and exclusion, to mean that such laws must at least survive a review for reasonableness. To date, the Supreme Court has not heeded scholarly calls for more exacting review of laws regulating alien entry. As described above, Mandel 's "facially legitimate and bona fide reason" test governs claims that an exclusion decision violates a U.S. citizen's constitutional rights. The Executive satisfies the test by identifying the statutory basis for the exclusion. However, the Executive may also have to disclose its factual basis for invoking a particular statute where the U.S. citizen challenger makes an "affirmative showing of bad faith." Despite the relatively clear picture of the scope of the Executive's exclusion power drawn from Mandel , Fiallo , and Din , three unresolved issues warrant discussion: (1) whether the Executive possesses inherent exclusion power, as opposed to solely statutory-based power; (2) the extent to which U.S. citizens or entities may challenge an alien's exclusion on statutory grounds; and (3) the extent to which the Constitution limits the Executive's application of broad delegations of congressional power to make exclusion determinations. The Supreme Court seems to have determined that the authority to exclude aliens reaches the Executive through congressional action alone, rather than through an inherent source of executive power. The text of the Constitution itself does not settle the question. Because the federal government's immigration power rests at least in part upon an "inherent power as a sovereign" not enumerated in the Constitution, courts cannot determine who owns the power by reading Article I or Article II. At least one pre- Mandel Supreme Court decision states that the Executive does possess inherent authority to exclude aliens. The case makes this statement, however, only in the context of a now-antiquated challenge to the constitutionality of congressional delegations of immigration authority to executive agencies. The case also acknowledges that, notwithstanding any inherent executive authority, in immigration matters the Executive typically acts upon congressional direction. Moreover, the weight of Supreme Court precedent assigns the immigration power to Congress rather than the Executive. Din and Mandel illustrate this point perhaps most clearly: even though both cases considered the constitutionality of executive action, they spoke only of statutory sources of executive authority. Because executive exclusion power derives primarily from legislative enactment, the Executive's decision to exclude an alien is susceptible in theory to attack on the grounds that the decision violates the governing statutes. In cases pressed by U.S. citizens, some lower courts have, on statutory grounds, rejected or called into question visa denials. In these cases, the courts have not applied Mandel 's deferential "facially legitimate and bona fide reason" test when reviewing the government's determination that a particular statutory provision required the denial of a visa application; instead, the courts have approached that statutory question as they would outside of the immigration context. As a result, these cases have analyzed the government's justifications for excluding aliens much more closely than the Supreme Court analyzed the constitutional claims in Mandel and Din . Supreme Court precedent offers limited guidance as to whether such statutory claims are cognizable and, if so, what standard of review should govern them. On the one hand, in recognizing that U.S. citizens could challenge exclusion decisions despite the bar against such suits when brought by aliens, Mandel and Din spoke narrowly of constitutional claims by U.S. citizens. Thus, one could read the cases to imply disapproval of statutory claims by U.S. citizens against exclusion decisions. On the other hand, even though the Supreme Court has never expressly endorsed statutory challenges to visa denials or other exclusion decisions concerning aliens outside the United States, it has reviewed statutory claims in arguably similar contexts. In Sale v. Haitian Centers Council , the Court considered and ultimately rejected statutory challenges to the U.S. Coast Guard's interdiction and forced return of Haitian migrants trying to reach the United States by sea. Specifically, the Court analyzed whether the interdictions violated the INA provision requiring immigration authorities to consider potential asylum or withholding of removal claims of arriving aliens before returning them to their place of origin. Similarly, in Jean v. Nelson , the Court considered whether the Immigration and Naturalization Service had violated its own regulations in denying immigration parole to a group of arrivals from Haiti who were detained in Florida pending a decision on their admissibility. In both cases, the Supreme Court reviewed the statutory and regulatory issues without applying Mandel or any other deferential standard of review. Both cases, however, concerned aliens in the government's control and resulting issues about the proper treatment of those aliens, rather than the issue of exclusion alone. On balance, a certain level of statutory analysis may sometimes inhere in judicial consideration of constitutional claims against exclusion decisions. Statutory and constitutional challenges do not always lend themselves to clear separation. Under the doctrine of constitutional avoidance, for example, courts strive to avoid "serious constitutional questions" through reasonable construction of underlying statutes or regulations. The Supreme Court invoked this doctrine in the exclusion context when it construed agency regulations to mean that returning LPRs could not be denied entry without a hearing. As one jurist noted in a visa denial case, courts cannot practicably review some constitutional claims without construing the relevant statutes first. Thus, principles of federal court jurisprudence probably require courts to consider statutory arguments against exclusion decisions to some extent, although perhaps only when constitutional claims point up those statutory arguments. The question that remains open, however, is what standard of review should govern such statutory arguments and, more specifically, whether courts may conduct a more exacting analysis of the government's justifications when the challenges against an alien's exclusion are styled as statutory rather than constitutional. An issue remains as to what limitations the Constitution imposes on the Executive's manner of implementing broad delegations of congressional exclusion authority. Justice Kennedy concluded in Din that the plenary nature of Congress's power to exclude aliens means that an executive exclusion decision for a statutory reason is facially legitimate and bona fide. But what about where Congress transfers its exclusion power to the Executive with few limiting criteria? What constitutional restrictions does the Executive face in that scenario? As Justice Kennedy observed in Din , Mandel itself raised this issue. There, the statute gave the Attorney General broad discretion to waive the communism-based ground for exclusion. In addressing the constitutional claim against the denial of Mandel's waiver, the Court assumed that Congress had the authority to exclude communists based on their political ideas, but the Court nonetheless proceeded to analyze whether the Attorney General had violated the First Amendment by denying Mandel's waiver because of his political ideas. This approach implies that the First Amendment could potentially limit the Attorney General's, but not Congress's, power to exclude based on political belief. Put differently, Mandel implies that congressional delegations of exclusion authority may not transfer the full scope of Congress's plenary power over such matters. Of course, Mandel sustained the waiver denial at issue and expressly left open the question whether it would have done so even if the government had declined to justify its action or justified it on less innocuous grounds. The case does at least suggest the possibility, however, that the Constitution limits the Executive's exclusion choices in a way that it does not limit Congress's. At the very least, the reasonableness requirement that appears to limit legislative action following Fiallo would also extend to executive implementation of broad delegations of legislative exclusion authority. President Trump set forth what has become known colloquially as the "Travel Ban" in two iterations of an executive order titled "Protecting the Nation from Foreign Terrorist Entry into the United States." The second order (EO-2), issued on March 6, 2017, revised and revoked the first (EO-1), issued on January 27, 2017, after the Ninth Circuit upheld an injunction against the first order. The two orders are similar but not identical; as discussed below, the Trump Administration narrowed the scope of EO-2 in response to the Ninth Circuit decision. As its primary source of statutory authority, EO-2 relies upon Section 212(f) of the INA, which allows the President to suspend the entry of any class of aliens where such entry would be "detrimental to the interests of the United States." EO-2's stated purpose is to protect the United States from terrorist acts perpetrated by foreign nationals. EO-2 imposed temporary bars on the entry of two classes of aliens located outside the United States: (1) foreign nationals from six countries (Iran, Libya, Somalia, Sudan, Syria, and Yemen), for 90 days following the order; and (2) refugees, for 120 days. These entry restrictions, according to the text of EO-2, aim to reduce administrative burdens on executive agencies while they conduct an assessment of current screening procedures for visa applicants and refugees. The restrictions exempt certain categories of aliens from their scope, including LPRs, and are also subject to waiver on a case-by-case basis. A group of plaintiffs—including states, organizations, and individual U.S. citizens and LPRs—contend that EO-2's true purpose is to exclude Muslims from the United States. The plaintiffs argue that the order therefore violates the Establishment Clause of the First Amendment and exceeds the scope of the President's statutory authority. They base the contention of anti-Muslim animus primarily upon statements that President Trump and his advisers made during the 2016 presidential campaign concerning the implementation of a "Muslim ban" on travel to the United States. The U.S. Courts of Appeals for the Fourth and Ninth Circuits upheld district court injunctions against EO-2's entry restrictions in their entirety—the Fourth Circuit on Establishment Clause grounds and the Ninth Circuit on statutory grounds. In contrast, at least one federal district court denied a motion to enjoin EO-2 after concluding that the order was likely lawful. The Supreme Court granted certiorari to hear both the Fourth and Ninth Circuit cases in the 2017 October Term. The Supreme Court also limited the lower court injunctions to allow the government to apply EO-2's entry restrictions against aliens who do not have a "bona fide relationship" to a person or entity within the United States. The Court left the injunctions in place with respect to aliens who have such relationships. Importantly (for the litigation, though not for the underlying issues of immigration law), the Court also drew attention to the issue whether the temporary entry restrictions would expire before the Court could decide the two cases, thereby rendering the cases moot. A subsequent event has brought the mootness issue even more into the forefront. On September 24, 2017, the President issued a proclamation that modified EO-2's 90-day entry restrictions on persons from the six listed countries. The proclamation deleted one country (Sudan) and added three others (Chad, North Korea, and Venezuela) from the list of affected countries; made the restrictions indefinite; and also modified the scope of the restrictions for persons from several of the countries. The proclamation does not appear to alter EO-2's restrictions on refugee entry. The day after the President issued the proclamation, the Supreme Court cancelled the scheduled oral argument in the Travel Ban cases and ordered the parties to submit briefs on whether the proclamation rendered the cases moot. Thus, it seems that the Supreme Court will, at the very least, carefully consider whether the claims in the Travel Ban cases are moot or whether other considerations make a decision on the merits of those claims inappropriate. Although the Travel Ban cases pose novel questions about the scope of the President's power to exclude aliens, some aspects of the litigation thus far have reaffirmed basic principles of the Supreme Court's immigration jurisprudence. First, the crucial distinction in that jurisprudence between LPRs and all other aliens—and to a lesser extent, between aliens physically present in the United States and aliens abroad—had a major impact on the EO-1 litigation and did much to shape the President's revisions to EO-2. EO-1 covered a broader group of aliens than does EO-2. Specifically, EO-1 applied not only to nonresident aliens abroad, but also was understood by reviewing courts to cover LPRs (inside and outside the country) and aliens other than LPRs who were already present in the United States on valid visas. This coverage beyond the core of the exclusion power described in Supreme Court precedent became a focus in the cases about EO-1's lawfulness. Most notably, when the Ninth Circuit upheld the temporary restraining order against EO-1, it emphasized that the order's applicability to LPRs and other aliens already present in the United States likely violated due process. EO-2, which the government crafted with the Ninth Circuit decision in mind, sought to repair this constitutional infirmity by carefully limiting the applicability of its entry restrictions to nonresident aliens only, and to only those nonresident aliens not physically present in the United States and without valid visas. As a result, the due process issues concerning LPRs and physically present nonresident aliens that arose in the EO-1 cases largely fell out of the EO-2 challenges. Second, the contours of the litigation thus far have been influenced by the rule that nonresident aliens outside the United States cannot challenge their exclusion from the United States in federal court. The identities of the plaintiffs in both Travel Ban cases reflect this rule: their ranks include states, U.S. organizations, and U.S. citizens and LPRs, but not any excluded nonresident aliens themselves. At no juncture has the litigation challenged the proposition that such aliens cannot press their own claims with respect to entry. Moreover, the Supreme Court's June 26 per curiam opinion seemed to rely on this proposition as the basis of the "bona fide relationship" test that it adopted to limit the injunctions against EO-2 pending resolution of the Travel Ban cases. The exclusion of aliens who do not have bona fide relationships with persons or entities in the United States, the Court reasoned, could not form the basis of a claim under Mandel . The litigation's conformity thus far with the doctrine against nonresident alien claims for entry has, in turn, given rise to the litigation's major threshold issue: whether the plaintiffs have suffered cognizable injuries from EO-2's entry restrictions sufficient to give them standing to sue. The U.S. government contends, in short, that plaintiffs do not adequately assert violations of their own rights (and therefore do not have standing) because EO-2 affects them only indirectly, through the exclusion of others. Both circuit courts, however, held that certain U.S. citizen and LPR plaintiffs with relatives in the six listed countries have standing based on the prolonged familial separation that EO-2 would likely cause them. This conclusion drew a dissenting opinion in the Fourth Circuit. The contested nature of the standing issue shows the obstacles that U.S.-citizen (or LPR) plaintiffs face in stating claims under Mandel against exclusion orders that do not actually apply to them. In this regard, the government's arguments against standing in the Travel Ban cases echo Justice Scalia's conclusion in Din that the denial of a visa to a nonresident alien does not burden the due process rights of that alien's American spouse. But while the Travel Ban litigation has tracked in some ways the basic tenets of long-standing immigration jurisprudence, it has also produced something unique: a Supreme Court opinion that upholds a measure of relief against the exclusion of nonresident aliens outside the United States, provided those aliens have a "bona fide relationship" with persons or entities within the country. To be sure, the Court did not at all consider the merits of the challenges to EO-2's entry restrictions in its June 26 per curiam decision. Rather, the Court arrived at the "bona fide relationship" rule as the interim measure that, in the Court's view, imposed the most equitable balance between the government's and the plaintiffs' interests pending the outcome of the litigation. Nonetheless, the prospect of a Supreme Court decision upholding—even temporarily, even in part, and even on equitable rather than legal grounds—an injunction against the executive branch's exclusion of nonresident aliens abroad might have struck some immigration law observers as unlikely before the outset of the Travel Ban controversy, particularly in the aftermath of the Din decision. The Establishment Clause of the First Amendment states that "Congress shall make no law respecting an establishment of religion." The Supreme Court's interpretations of this language have given rise to one of the most complex areas of constitutional law, with an array of standards fashioned for discrete categories of government action such as legislative prayer, school prayer, and religious displays on public property. However, the various strains of jurisprudence generally (though not universally) agree on one point: the government violates the Establishment Clause if it undertakes official action with the purpose of favoring or disfavoring a particular religion. The Fourth Circuit and multiple district courts applied this rule to hold that EO-2 likely violates the Establishment Clause because, in the view of these courts, the purpose of the order is to exclude Muslims from the United States. At least one district court, on the other hand, has agreed with the government's position that EO-2 likely does not violate the Establishment Clause. Before considering how the exclusion jurisprudence applies to the constitutional claim against EO-2, one should understand that the Supreme Court could ultimately resolve that claim without applying Mandel or considering the immigration context. Mandel and Din bear upon the Establishment Clause question because they instruct courts to limit the depth of their constitutional inquiry when dealing with executive decisions to exclude aliens. In contrast, the Supreme Court's Establishment Clause jurisprudence concerning government actions unrelated to immigration would appear to allow a much closer level of scrutiny than the exclusion cases. The Establishment Clause jurisprudence has on occasion rejected the government's proffered, secular justifications and invalidated laws or actions based on evidence of other, religiously oriented motives. The plaintiffs in the Travel Ban cases rely heavily on evidence beyond the face of the government's proffered justifications; most notably, they rely on campaign statements as evidence that anti-Muslim animus motivated EO-2. The government, however, has argued throughout the litigation that not even the Establishment Clause cases condone judicial searches for government purpose in campaign discourse. In essence, the government's argument is that EO-2, which does not on its face single out Muslims, survives a stricter level of review than Mandel requires. A Supreme Court decision on Establishment Clause principles, without addressing Mandel , would arguably comport with the Court's previous efforts to keep its pronouncements as narrow as possible when addressing the outer reaches of the political branches' power to exclude aliens. The discussion below analyzes the Establishment Clause claim against EO-2 under the Supreme Court's exclusion jurisprudence. There are three primary questions: (1) whether the Mandel standard governs the constitutional analysis of EO-2; (2) whether Mandel , if it does govern, permits consideration of evidence of government purpose beyond the text of EO-2; and (3) whether extrinsic evidence of anti-Muslim animus, if it can be considered, demonstrates an Establishment Clause violation. The Supreme Court has applied Mandel 's "facially legitimate and bona fide" standard—or a version of that standard adapted to the legislative context—to three different types of constitutional claims: free speech ( Mandel ), equal protection ( Fiallo ), and due process ( Din ). The standard thus appears to apply to all constitutional challenges brought by U.S. persons or entities against executive exercise of the exclusion power. Accordingly, the issue of EO-2's constitutionality under the Establishment Clause appears to boil down to whether the government has supplied a "facially legitimate and bona fide" justification for the order. Agreement as to Mandel 's applicability to EO-2 is not, however, universal. At least two counterarguments exist. First, some courts have described Mandel as governing only challenges to individual visa denials, not broader executive policy. Dissenting judges have pointed out that this argument may be difficult to square with Fiallo , which relied on Mandel in upholding a gender-discriminatory immigration statute. Indeed, Fiallo described its analytical approach to the statute as an effort to apply something approximating the Mandel standard of review to a "broad congressional policy choice." Another argument for why Mandel should not govern the Establishment Clause claim has surfaced in legal commentary. According to some commentators, the Establishment Clause, unlike individual rights such as free speech and equal protection, creates a structural limitation on the scope of government action rather than an individual right against certain forms of government regulation. According to this argument, a religiously discriminatory government exclusion policy effects an establishment of religion as much as a parallel domestic policy would, because the identity of the persons harmed by the policy (aliens or citizens) does not alter the constitutional limitation. In other words, by the terms of the argument, it does not matter for Establishment Clause purposes whether the government hangs a sign stating its religious preferences at the border or in the interior—both statements violate the structural rule of religious neutrality. This argument does not find direct support in any Supreme Court cases. But, on the other hand, the Supreme Court has never actually applied Mandel to an Establishment Clause claim or otherwise considered the extent to which the Establishment Clause may limit the exclusion power. If the Court were inclined to apply closer constitutional scrutiny to EO-2 than it applied in Mandel , Din , and Fiallo , the arguably structural nature of the Establishment Clause guarantee could serve as a basis for distinguishing those cases. Such a distinction would arguably follow the mold of Morales-Santana , which also relied on a distinction not previously considered salient (derivative citizenship statutes versus immigration statutes) in determining not to apply Fiallo . If Mandel does govern the Establishment Clause claim against EO-2, the principal question becomes whether it permits consideration of evidence of the President's purpose beyond the face of EO-2 itself. Most reviewing courts, including those that have ruled that EO-2 likely violates the Establishment Clause, have concluded that the order does not have an expressly discriminatory purpose. The order purports to exclude aliens from countries that are "state sponsor[s] of terrorism, ha[ve] been significantly compromised by terrorist organizations, or contain[] active combat zones." The order does not, according to most courts, purport to exclude Muslims. But the plaintiffs assert that extrinsic evidence shows that during the presidential campaign, then-candidate Donald Trump considered excluding aliens based on their religion, and the courts that have determined that EO-2 likely violates the Establishment Clause have relied heavily upon this extrinsic evidence. The strength of the Establishment Clause claim under Mandel , therefore, appears to turn upon the scope of reviewable evidence. On the one hand, Mandel and Din may be read to provide much support for those who argue that the Court should limit its review to the face of EO-2. Mandel itself instructed courts not to "look behind" the Executive's stated reason for excluding an alien, and it did so in the face of a government justification that the petitioners argued included indications of pretext. Just as the Court declined to scrutinize the Attorney General's explanation that he had denied Mandel's visa because of his prior visa abuse and not because of his political views, the argument goes, so too should the Court decline to probe the express purpose of EO-2. Similarly, in his Din opinion, Justice Kennedy required nothing more of the government than a statutory citation to sustain a visa denial under a terrorism-related ineligibility. Justice Kennedy did not examine the government's evidentiary basis for applying the statute. Because EO-2 likewise cites a statutory source of exclusion power—INA § 212(f)—the government and some jurists contend that EO-2, too, should be sustained without further inquiry against the Establishment Clause challenge. The counterargument, and the analysis that guided the Fourth Circuit decision, rests on the "bona fide" prong of the Mandel test. Because the Fourth Circuit concluded that ample evidence suggests that EO-2's stated purpose is a bad-faith pretext for religious discrimination, the court reasoned that it need not accept that stated purpose. Under this reasoning, upon such an affirmative showing of bad faith, courts must cast aside the deferential Mandel test and apply the same level of constitutional scrutiny they would apply outside of the immigration context. For an Establishment Clause claim such as the one asserted against EO-2, such standard scrutiny encompasses consideration of the "historical context" and the "specific sequence of events" that led to the order's passage. The Fourth Circuit held that those categories of information include statements about a potential "Muslim Ban" that then-candidate Donald Trump made during the 2016 campaign. Dissenting judges and the government have criticized the Fourth Circuit's approach to the "bona fide" prong as circular, because it relies upon evidence beyond the face of EO-2 to make a determination about whether to consider evidence beyond the face of EO-2. The Fourth Circuit majority opinion that employs this analysis does, to some extent, give the impression of addressing the same question twice. Nonetheless, the analysis finds some support in Justice Kennedy's statement in Din that courts should not look beyond the face of the government's proffer "absent an affirmative showing of bad faith." Justice Kennedy did not have occasion to apply that statement of law to fact, and his opinion in Din garnered only two votes. His choice of language, however, might be construed to contemplate judicial consideration of a plaintiff's proffer of extrinsic bad faith evidence, and the Fourth Circuit in fact construed the language this way. On balance, consideration of campaign statements and other extrinsic evidence of EO-2's purpose would certainly exceed the scope of the review that the Supreme Court conducted in Mandel and Din . In those cases, the Court did not probe the government's stated justifications for excluding the aliens in question. The allegations of religious animus in the Travel Ban cases arguably present unique facts, however, and the Supreme Court has yet to clarify what the "bona fide" prong of the Mandel test means in application. If the Court reaches the merits and applies Mandel , the scope of its review will probably depend on whether it determines (1) that a bad faith exception exists to Mandel 's rule against looking behind the government's justification for excluding aliens; and (2) if so, that the Travel Ban case facts trigger the exception. In the Travel Ban cases, the government does not argue that the President has authority to exclude aliens based on their religion. Perhaps for this reason, those reviewing courts that have deemed it appropriate to consider campaign statements and other extrinsic evidence of EO-2's allegedly anti-Muslim purpose have generally held that the order violates the Establishment Clause. In the only example of a case that considered extrinsic evidence but ruled in the government's favor, a federal district court held that the extrinsic evidence did not suffice to show discriminatory purpose. Even there, however, the district court seemed to assume that EO-2 would violate the Establishment Clause if it had a religiously discriminatory purpose. This litigation posture—the absence of any contention that the President may exclude aliens based on religion—creates an interesting contrast with Mandel . There, the unchallenged assumption cut the other way: that Congress had the power to exclude aliens based on their political belief. The executive branch argued that it, too, could exercise congressionally delegated exclusion authority to deny entry based on political belief or for "any reason or no reason." The Mandel Court adopted the "facially legitimate and bona fide" standard to avoid addressing this contention. Thus, Mandel and the Travel Ban cases start from inverted executive branch contentions about the scope of its exclusion power. In Mandel , the executive branch contended that it possessed, through legislative delegation, Congress's uncontested (in that case) power to exclude aliens based on political belief. In the Travel Ban cases, in contrast, the executive branch seems to tacitly concede that it does not have power to exclude based on religion. The upshot of both cases might remain the same, however. The Supreme Court likely will not address the underlying question about the outer limits of the executive power. In Mandel , the Court used the "facially legitimate and bona fide" standard to avoid answering whether the Executive could deny waivers based on political belief. In the Travel Ban cases, the Supreme Court probably will not answer directly whether the executive branch can exclude aliens based on religion, because the executive branch does not argue this point. The statutory arguments against EO-2 boil down to the contention that the entry restrictions set forth in the order exceed the scope of the President's authority to exclude aliens under the INA. On this statutory theory, the Ninth Circuit concluded that EO-2 is likely unlawful, as did three concurring judges in the Fourth Circuit. This section briefly summarizes the three principal statutory arguments against EO-2 and how lower courts have addressed those arguments. The section then analyzes an issue that the Supreme Court might confront in addressing the statutory challenges: identifying the appropriate standard of review. A preliminary point: the statutory and constitutional claims against EO-2 may not operate entirely independently of each other. Through the canon of constitutional avoidance, the Supreme Court's approach to the Establishment Clause claim raised against EO-2 may influence the Court's resolution of the statutory claims. If the Supreme Court entertains serious doubts about EO-2's constitutionality, the Court might assess whether EO-2 violates the underlying statutes under any "fairly possible" interpretation before striking the order down as a violation of the Establishment Clause. The Ninth Circuit appeared to take this approach, although it did not invoke the avoidance canon clearly. One of the Fourth Circuit concurring opinions, in contrast, expressly framed its statutory analysis as a method for avoiding a serious Establishment Clause question. There are three principal arguments raised in the Travel Ban litigation that EO-2 exceeds the scope of the President's statutory authority: 1. The President did not properly invoke his authority under INA § 212(f). That provision gives the President power to exclude "any class of aliens," but only if he finds that the entry of such aliens "would be detrimental to the interests of the United States." EO-2, it is argued, does not evince an adequate finding that the entry of the aliens it seeks to bar would be "detrimental." 2. EO-2's exclusion of citizens of the six listed countries violates INA § 202(a)(1)(A), which prohibits discrimination based on nationality in the issuance of immigrant visas. 3. EO-2's reduction in the FY2017 refugee cap from 110,000 to 50,000 refugees violates INA § 207, which establishes specific procedures—including consultation with Congress—for establishing the annual refugee cap. Of the three arguments, only the first applies to the full scope of EO-2's entry restrictions. The basis of the argument is that INA § 212(f) contains a prerequisite: the President must find that the entry of a class of aliens would be "detrimental" to invoke the exclusion authority that the statute delegates to him. EO-2 attempts to satisfy the prerequisite with findings about the presence of terrorist organizations and conditions of instability within the six restricted countries. The order concludes that such conditions within the identified countries increase the likelihood that "terrorist operatives or sympathizers" could enter the United States from those locations. The order also provides examples of persons implicated in terrorism-related crimes who were admitted to the United States as refugees. The Ninth Circuit, and some of the Fourth Circuit concurring opinions, rejected these justifications as inadequate. The circuit courts concluded that EO-2 does not demonstrate a link between an individual alien's nationality and the alien's propensity to engage in terrorism, and that the order does not explain why current visa and refugee screening procedures do not suffice to address the risk of terrorist entry. The government, for its part, argues that the Ninth Circuit's rejection of the President's articulated justifications for the EO-2 entry restrictions showed an improper failure to defer to the President's national security determinations. The second and third statutory arguments are more limited. The second argument, concerning INA § 202(a)(1)(A), only applies to citizens of the six listed countries who seek entry as immigrants rather than nonimmigrants (i.e., aliens authorized to permanently reside in the United States versus those permitted to remain in the country on a temporary basis). In other words, the argument is that EO-2 violates the INA by denying entry based on nationality to prospective immigrants from the six restricted countries, and that argument would not impact the lawfulness of EO-2's applicability to prospective nonimmigrants from those countries. The third argument, concerning the refugee admissions procedures in INA § 207, applies only to EO-2's reduction in refugee admissions. The two arguments proceed on the premise that specific provisions in the INA limit the scope of the President's exclusion authority under § 212(f), even though § 212(f) does not impose such limitations itself. The Ninth Circuit agreed with this premise, concluding that both § 202(a)(1)(A) and § 207 limit the President's § 212(f) authority—and that EO-2 violates those limitations—because the former two statutes were enacted after § 212(f) and are more specific than § 212(f). Other judges have rejected the § 202(a)(1)(A) argument on the reasoning that its nondiscrimination bar applies only to immigrant visa decisions, not entry restrictions. Put differently, these judges have reasoned that EO-2's denial of entry to immigrants from the six restricted countries based on their nationality does not run afoul of § 202(a)(1)(A)'s prohibition of the denial of visas based on nationality. As for the § 207 argument concerning refugee admissions, the Ninth Circuit's agreement with the argument marks the only judicial consideration of it thus far. In response to both the § 202(a)(1)(A) and the § 207 arguments, the government contends primarily that § 212(f) can and should be interpreted to harmonize with the other two statutes, because § 202(a)(1)(A) does not restrict denials of entry and the § 207 procedures for setting the annual refugee cap do not restrict the President's ability to limit (rather than expand) refugee admissions mid-year. The statutory arguments against EO-2 raise an unresolved question: should the courts defer to the President's evidentiary basis for invoking his exclusion authority under INA § 212(f)? If so, what standard of deference should apply? For the Establishment Clause claims, these questions have reasonably clear answers under existing case law. Mandel and Di n establish that the "facially legitimate and bona fide" standard of review governs constitutional challenges to an alien's exclusion. In contrast, as noted above, the Supreme Court has never explained what standard of review— Mandel or something else—applies to a U.S. person or entity's claim that the exclusion of an alien violates a statute. In reaching its determination that EO-2 likely violates the INA, the Ninth Circuit concluded that Mandel did not govern its analysis of the statutory claims against the order. The conclusion proved significant, as it led the court to apply an exacting standard of review to the government's justifications. The Ninth Circuit determined that EO-2 does not "bridge the gap" between the country conditions it describes (terrorist activity and instability) and the individual aliens from those countries that the order excludes. In other words, according to the Ninth Circuit, the order's use of a broad classification (nationality) to exclude aliens does not match the justification (to prevent terrorist acts) with sufficient precision. This analysis resembles what is known as strict judicial scrutiny in constitutional jurisprudence. It demands much more of the government's justification for its measures than did the level of deference the Supreme Court applied when considering constitutional claims in Mandel and Din . A reviewing court might identify multiple factors to explain why statutory challenges to an alien's exclusion should draw closer scrutiny of government justifications than corresponding constitutional challenges. Perhaps the heightened scrutiny of statutory claims results from the application of constitutional avoidance, which a deferential level of statutory review could hamper. Or, as the Ninth Circuit proposed, perhaps heightened scrutiny should apply in situations where the Executive affirmatively invokes statutory authority to exclude otherwise eligible aliens, as President Trump did in EO-2, as opposed to situations where the Executive declines to invoke statutory waiver authority to admit ineligible aliens, as the Attorney General did in Mandel . The government, for its part, argues that the national security concerns underlying EO-2 require judicial deference to the President's factual basis for invoking § 212(f). Whatever the merit of these or other arguments, the Supreme Court has yet to endorse any of them. The appropriate standard of review for a statutory argument against exclusion remains an open issue. The Travel Ban cases implicate the nucleus of the political branches' immigration power: the power to deny entry to aliens abroad. The cases against EO-2, unlike the first wave of litigation challenging EO-1, concern only the exclusion of aliens physically outside the United States. The cases do not involve aliens at the border or aliens who have entered the country physically. Accordingly, the cases isolate the issue of the scope of the Executive's power to deny entry from the issue of what measures the Executive may lawfully take to carry out the exclusion of an alien already on American soil. The cases, in other words, concern a pure exclusion issue, and they could thus set the stage for a landmark statement from the Supreme Court about the political branches' plenary immigration power. If the plaintiffs win on the merits of their Establishment Clause claim, and to a lesser extent on their statutory claims, their victory would represent a judicial check on executive exercise of the exclusion power unlike any in the Supreme Court's history. That check could come in the form of a distinction between legislative and executive power—i.e., that EO-2 is unlawful because it contravenes the INA—or as a clear holding that U.S. citizens' Establishment Clause rights limit the exclusion of nonresident aliens. A victory for the plaintiffs in the latter form would exceed prior Supreme Court limitations of the plenary power doctrine. On the other hand, if the government wins on the merits under application of Mandel deference, the decision (depending on its reasoning) could stand as a reaffirmation of the exceptional extent of the Executive's power to deny entry to nonresident aliens. A third outcome, however, seems equally viable: that the Supreme Court will not actually decide whether EO-2 exceeds the scope of the President's statutory or constitutional power. The Court could dismiss the government's appeals in the Travel Ban cases as moot or reject the plaintiffs' claims for lack of standing rather than decide them on the merits; or, maybe most in line with its approach in prior exclusion cases, the Court could decide the merits of the plaintiffs' claims in a way that does not require it to define the boundaries of the Executive's power, such as by rejecting the claims under domestic Establishment Clause jurisprudence. In prior exclusion cases concerning the rights of U.S. citizens, the Court has preferred such narrow grounds of decision that do not require a defining statement about if and where the plenary power ends. If the Court adopts this approach or does not decide for other reasons the merits of the Travel Ban cases, the June 26 per curiam decision limiting the Executive's power to exclude aliens with "bona fide relationships" to U.S. persons or entities will remain in the case reporters as a unique example of judicial involvement in exclusion decisions. But because that decision avoids any discussion of the merits of the claims against EO-2, it probably will not itself change how courts review U.S. citizen challenges to the exclusion of nonresident aliens abroad in the future.

Summary: The Supreme Court has determined that inherent principles of sovereignty give Congress "plenary power" to regulate immigration. The core of this power—the part that has proven most impervious to judicial review—is the authority to determine which aliens may enter the country and under what conditions. The Court has determined that the executive branch, by extension, has broad authority to enforce laws concerning alien entry mostly free from judicial oversight. Two principles frame the scope of the political branches' power to exclude aliens. First, nonresident aliens abroad cannot challenge exclusion decisions because they do not have constitutional or statutory rights with respect to entry. Second, even when the exclusion of a nonresident alien burdens the constitutional rights of a U.S. citizen, the government need only articulate a "facially legitimate and bona fide" justification to prevail against the citizen's constitutional challenge. The first principle is the foundation of the Supreme Court's immigration jurisprudence, so well established that the Court has not had occasion to apply it directly in recent decades. The second principle, in contrast, has given rise to the Court's modern exclusion jurisprudence. In three important cases since 1972—Kleindienst v. Mandel, Fiallo v. Bell, and the splintered Kerry v. Din—the Court applied the "facially legitimate and bona fide" test to deny relief to U.S. citizens who claimed that the exclusion of certain aliens violated the citizens' constitutional rights. In each case, the Court accepted the government's stated reasons for excluding the aliens without scrutinizing the underlying facts. This deferential standard of review effectively foreclosed the U.S. citizens' constitutional challenges. Nonetheless, the Court refrained in all three cases from deciding whether the power to exclude aliens has any limitations. Particularly with regard to the executive branch, the Court left an unexplored margin at the outer edges of the power. In March 2017, President Trump issued an executive order temporarily barring many nationals of six Muslim-majority countries and all refugees from entering the United States, subject to limited waivers and exemptions. This order replaced an earlier executive order that a federal appellate court had enjoined as likely unconstitutional. Upon challenges brought by U.S. citizens and entities, two federal appellate courts determined that the revised order is likely unlawful, one under the Establishment Clause of the First Amendment and the other under the Immigration and Nationality Act (INA). The Supreme Court agreed to review those cases and, for the meantime, has ruled that the Executive may not apply the revised order to exclude aliens who have a "bona fide relationship" with a U.S. person or entity. In reaching this interim solution, the Supreme Court considered only equitable factors and carefully avoided any discussion of the merits of the constitutional and statutory challenges against the revised order. Even so, the Court's temporary restriction of the executive power to exclude nonresident aliens abroad is remarkable when compared with the Court's earlier immigration jurisprudence. The merits of these so-called "Travel Ban" cases raise significant questions about the extent to which the rights of U.S. citizens limit the executive power to exclude aliens. It seems relatively clear that, under existing jurisprudence, the "facially legitimate and bona fide" standard should govern the Establishment Clause claims against the revised executive order. However, Supreme Court precedent does not clarify whether that standard contains an exception that might permit courts to test the government's proffered justification for an exclusion by examining the underlying facts in particular circumstances. Nor does Supreme Court precedent resolve whether the standard governs U.S. citizens' statutory claims against executive exercise of the exclusion power, or even whether such statutory claims are cognizable. The outcome of the Travel Ban cases would likely turn upon these issues, if the Supreme Court were to decide the cases on the merits rather than on a threshold question such as mootness (a key issue in light of a presidential proclamation modifying the entry restrictions at issue in the cases).