Holder v. Humanitarian Law Project

delivered the opinion of the Court.

Congress has prohibited the provision of “material support or resources” to certain foreign organizations that engage in terrorist activity. 18 U. S. C. § 2339B(a)(l). That prohibition is based on a finding that the specified organizations “are so tainted by their criminal conduct that any contribution to such an organization facilitates that conduct.” Anti-terrorism and Effective Death Penalty Act of 1996 (AEDPA), § 301(a)(7), 110 Stat. 1247, note following 18 U. S. C. §2339B (Findings and Purpose). The plaintiffs in this litigation *8seek to provide support to two such organizations. Plaintiffs claim that they seek to facilitate only the lawful, nonviolent purposes of those groups, and that applying the material-support law to prevent them from doing so violates the Constitution. In particular, they claim that the statute is too vague, in violation of the Fifth Amendment, and that it infringes their rights to freedom of speech and association, in violation of the First Amendment. We conclude that the material-support statute is constitutional as applied to the particular activities plaintiffs have told us they wish to pursue. We do not, however, address the resolution of more difficult cases that may arise under the statute in the future.

I

This litigation concerns 18 U. S. C. § 2339B, which makes it a federal crime to “knowingly provid[e] material support or resources to a foreign terrorist organization.”1 Congress has amended the definition of “material support or resources” periodically, but at present it is defined as follows:

“[T]he term “material support or resources’ means any property, tangible or intangible, or service, including currency or monetary instruments or financial securities, financial services, lodging, training, expert advice or assistance, safehouses, false documentation or identification, communications equipment, facilities, *9weapons, lethal substances, explosives, personnel (1 or more individuals who may be or include oneself), and transportation, except medicine or religious materials.” § 2339A(b)(l); see also § 2339B(g)(4).

The authority to designate an entity a “foreign terrorist organization” rests with the Secretary of State. 8 U. S. C. §§ 1189(a)(1), (d)(4). She may, in consultation with the Secretary of the Treasury and the Attorney General, so designate an organization upon finding that it is foreign, engages in “terrorist activity” or “terrorism,” and thereby “threatens the security of United States nationals or the national security of the United States.” §§ 1189(a)(1), (d)(4). “‘[N]ational security’ means the national defense, foreign relations, or economic interests of the United States.” § 1189(d)(2). An entity designated a foreign terrorist organization may seek review of that designation before the D. C. Circuit within 30 days of that designation. § 1189(e)(1).

In 1997, the Secretary of State designated 30 groups as foreign terrorist organizations. See 62 Fed. Reg. 52650. Two of those groups are the Kurdistan Workers’ Party (also known as the Partiya Karkeran Kurdistan, or PKK) and the Liberation Tigers of Tamil Eelam (LTTE). The PKK is an organization founded in 1974 with, the aim of establishing an independent Kurdish state in southeastern Turkey. Humanitarian Law Project v. Reno, 9 F. Supp. 2d 1176, 1180-1181 (CD Cal. 1998); Brief for Petitioners in No. 08-1498, p. 6 (hereinafter Brief for Government). The LTTE is an organization founded in 1976 for the purpose of creating an independent Tamil state in Sri Lanka. 9 F. Supp. 2d, at 1182; Brief for Government 6. The District Court in this action found that the PKK and LTTE engage in political and humanitarian activities. See 9 F. Supp. 2d, at 1180-1182. The Government has presented evidence that both groups have also committed numerous terrorist attacks, some of which have harmed American citizens. See App. 128-133. The LTTE sought judicial review of its designation as a for*10eign terrorist organization; the D. C. Circuit upheld that designation. See People’s Mojahedin Organization of Iran v. Department of State, 182 F. 3d 17, 18-19, 25 (1999). The PKK did not challenge its designation. 9 F. Supp. 2d, at 1180.

Plaintiffs in this litigation are two U. S. citizens and six domestic organizations: the Humanitarian Law Project (HLP) (a human rights organization with consultative status to the United Nations); Ralph Fertig (the HLP’s president, and a retired Administrative Law Judge); Nagalingam Jeyalingam (a Tamil physician, born in Sri Lanka and a naturalized U. S. citizen); and five nonprofit groups dedicated to the interests of persons of Tamil descent. Brief for Petitioners in No. 09-89, pp. ii, 10 (hereinafter Brief for Plaintiffs); App. 48. In 1998, plaintiffs filed suit in federal court challenging the constitutionality of the material-support statute, § 2339B. Plaintiffs claimed that they wished to provide support for the humanitarian and political activities of the PKK and LTTE in the form of monetary contributions, other tangible aid, legal training, and political advocacy, but that they could not do so for fear of prosecution under §2339B. 9 F. Supp. 2d, at 1180-1184.2

As relevant here, plaintiffs claimed that the material-support statute was unconstitutional on two grounds: First, it violated their freedom of speech and freedom of association under the First Amendment, because it criminalized their *11provision of material support to the PKK and LTTE, without requiring the Government to prove that plaintiffs had a specific intent to further the unlawful ends of those organizations. Id., at 1184. Second, plaintiffs argued that the statute was unconstitutionally vague. Id., at 1184-1185.

Plaintiffs moved for a preliminary injunction, which the District Court granted in part. The District Court held that plaintiffs had not established a probability of success on their First Amendment speech and association claims. See id., at 1196-1197. But the court held that plaintiffs had established a probability of success on their claim that, as applied to them, the statutory terms “personnel” and “training” in the definition of “material support” were impermissibly vague. See id., at 1204.

The Court of Appeals affirmed. 205 F. 3d 1130, 1138 (CA9 2000). The court rejected plaintiffs’ speech and association claims, including their claim that § 2339B violated the First Amendment in barring them from contributing money to the PKK and LTTE. See id., at 1133-1136. But the Court of Appeals agreed with the District Court that the terms “personnel” and “training” were vague because it was “easy to imagine protected expression that falls within the bounds” of those terms. Id., at 1138; see id., at 1137.

With the preliminary injunction issue decided, the action returned to the District Court, and the parties moved for summary judgment on the merits. The District Court entered a permanent injunction against applying to plaintiffs the bans on “personnel” and “training” support. See No. CV-98-1971 ABC (BQRx), 2001 WL 36105333 (CD Cal., Oct. 2, 2001). The Court of Appeals affirmed. 352 F. 3d 382 (CA9 2003).

Meanwhile, in 2001, Congress amended the definition of “material support or resources” to add the term “expert advice or assistance.” Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 (USA PATRIOT ACT), *12§ 805(a)(2)(B), 115 Stat. 377. In 2003, plaintiffs filed a second action challenging the constitutionality of that term as applied to them. 309 F. Supp. 2d 1185, 1192 (CD Cal. 2004).

In that action, the Government argued that plaintiffs lacked standing and that their preenforcement claims were not ripe. Id., at 1194. The District Court held that plaintiffs’ claims were justiciable because plaintiffs had sufficiently demonstrated a “genuine threat of imminent prosecution,” id., at 1195 (internal quotation marks omitted), and because § 2339B had the potential to chill plaintiffs’ protected expression, see id., at 1197-1198. On the merits, the District Court held that the term “expert advice or assistance” was impermissibly vague. Id., at 1201. The District Court rejected, however, plaintiffs’ First Amendment claims that the new term was substantially overbroad and criminalized associational speech. See id., at 1202, 1203.

The parties cross-appealed. While the cross-appeals were pending, the Ninth Circuit granted en banc rehearing of the panel’s 2003 decision in plaintiffs’ first action (involving the terms “personnel” and “training”). See 382 F. 3d 1154, 1155 (2004). The en banc court heard reargument on December 14, 2004. See 380 F. Supp. 2d 1134, 1138 (CD Cal. 2005). Three days later, Congress again amended §2339B and the definition of “material support or resources.” Intelligence Reform and Terrorism Prevention Act of 2004 (IRTPA), §6603, 118 Stat. 3762-3764.

In IRTPA, Congress clarified the mental state necessary to violate § 2339B, requiring knowledge of the foreign group’s designation as a terrorist organization or the group’s commission of terrorist acts. §2339B(a)(l). Congress also added the term “service” to the definition of “material support or resources,” § 2339A(b)(l), and defined “training” to mean “instruction or teaching designed to impart a specific skill, as opposed to general knowledge,” § 2339A(b)(2). It also defined “expert advice or assistance” to mean “advice or assistance derived from scientific, technical or other special*13ized knowledge.” § 2339A(b)(3). Finally, IRTPA clarified the scope of the term “personnel” by providing:

“No person may be prosecuted under [§2339B] in connection with the term ‘personnel’ unless that person has knowingly provided, attempted to provide, or conspired to provide a foreign terrorist organization with 1 or more individuals (who may be or include himself) to work under that terrorist organization’s direction or control or to organize, manage, supervise, or otherwise direct the operation of that organization. Individuals who act entirely independently of the foreign terrorist organization to advance its goals or objectives shall not be considered to be working under the foreign terrorist organization’s direction and control.” §2339B(h).

Shortly after Congress enacted IRTPA, the en banc Court of Appeals issued an order in plaintiffs’ first action. 393 F. 3d 902, 903 (CA9 2004). The en banc court affirmed the rejection of plaintiffs’ First Amendment claims for the reasons set out in the Ninth Circuit’s panel decision in 2000. See ibid. In light of IRTPA, however, the en banc court vacated the panel’s 2003 judgment with respect to vagueness, and remanded to the District Court for further proceedings. Ibid. The Ninth Circuit panel assigned to the cross-appeals in plaintiffs’ second action (relating to “expert advice or assistance”) also remanded in light of IRTPA. See 380 F. Supp. 2d, at 1139.

The District Court consolidated the two actions on remand. See ibid. The court also allowed plaintiffs to challenge the new term “service.” See id., at 1151, n. 24. The parties moved for summary judgment, and the District Court granted partial relief to plaintiffs on vagueness grounds. See id., at 1156.

The Court of Appeals affirmed once more. 552 F. 3d 916, 933 (CA9 2009). The court first rejected plaintiffs’ claim that the material-support statute would violate due process *14unless it were read to require a specific intent to further the illegal ends of a foreign terrorist organization. See id., at 926-927. The Ninth Circuit also held that the statute was not overbroad in violation of the First Amendment. See id., at 931-932. As for vagueness, the Court of Appeals noted that plaintiffs had not raised a “facial vagueness challenge.” Id., at 929, n. 6. The court held that, as applied to plaintiffs, the terms “training,” “expert advice or assistance” (when derived from “other specialized knowledge”), and “service” were vague because they “continue [d] to cover constitutionally protected advocacy,” but the term “personnel” was not vague because it “no longer criminalize[d] pure speech protected by the First Amendment.” Id., at 929-931.

The Government petitioned for certiorari, and plaintiffs filed a conditional cross-petition. We granted both petitions. 557 U. S. 966 (2009).

II

Given the complicated 12-year history of this litigation, we pause to clarify the questions before us. Plaintiffs challenge § 2339B’s prohibition on four types of material support— “training,” “expert advice or assistance,” “service,” and “personnel.” They raise three constitutional claims. First, plaintiffs claim that § 2339B violates the Due Process Clause of the Fifth Amendment because these four statutory terms are impermissibly vague. Second, plaintiffs claim that §2339B violates their freedom of speech under the First Amendment. Third, plaintiffs claim that §2339B violates their First Amendment freedom of association.

Plaintiffs do not challenge the above statutory terms in all their applications. Rather, plaintiffs claim that §2339B is invalid to the extent it prohibits them from engaging in certain specified activities. See Brief for Plaintiffs 16-17, n. 10. With respect to the HLP and Judge Fertig, those activities are: (1) “train[ing] members of [the] PKK on how to use humanitarian and international law to peacefully resolve disputes”; (2) “engaging] in political advocacy on behalf of *15Kurds who live in Turkey”; and (3) “teach[ing] PKK members how to petition various representative bodies such as the United Nations for relief.” 552 F. 3d, at 921, n. 1; see 380 F. Supp. 2d, at 1136. With respect to the other plaintiffs, those activities are: (1) “train[ing] members of [the] LTTE to present claims for tsunami-related aid to mediators and international bodies”; (2) “offering] their legal expertise in negotiating peace agreements between the LTTE and the Sri Lankan government”; and (3) “engag[ing] in political advocacy on behalf of Tamils who live in Sri Lanka.” 552 F. 3d, at 921, n. 1; see 380 F. Supp. 2d, at 1137.

Plaintiffs also state that “the LTTE was recently defeated militarily in Sri Lanka,” so “[m]uch of the support the Tamil organizations and Dr. Jeyalingam sought to provide is now moot.” Brief for Plaintiffs 11, n. 5. Plaintiffs thus seek only to support the LTTE “as a political organization outside Sri Lanka advocating for the rights of Tamils.” Ibid. Counsel for plaintiffs specifically stated at oral argument that plaintiffs no longer seek to teach the LTTE how to present claims for tsunami-related aid, because the LTTE now “has no role in Sri Lanka.” Tr. of Oral Arg. 63. For that reason, helping the LTTE negotiate a peace agreement with Sri Lanka appears to be moot as well. Thus, we do not consider the application of § 2339B to those activities here.

One last point. Plaintiffs seek preenforcement review of a criminal statute. Before addressing the merits, we must be sure that this is a justiciable case or controversy under Article III. We conclude that it is: Plaintiffs face “a credible threat of prosecution” and “should not be required to await and undergo a criminal prosecution as the sole means of seeking relief.” Babbitt v. Farm Workers, 442 U. S. 289, 298 (1979) (internal quotation marks omitted). See also MedImmune, Inc. v. Genentech, Inc., 549 U. S. 118, 128-129 (2007).

Plaintiffs claim that they provided support to the PKK and LTTE before the enactment of § 2339B and that they would provide similar support again if the statute’s allegedly un*16constitutional bar were lifted. See 309 F. Supp. 2d, at 1197. The Government tells us that it has charged about 150 persons with violating § 2339B, and that several of those prosecutions involved the enforcement of the statutory terms at issue here. See Brief for Government 5. The Government has not argued to this Court that plaintiffs will not be prosecuted if they do what they say they wish to do. Cf. Tr. of Oral Arg. 57-58. See Babbitt, supra, at 302. See also Milavetz, Gallop & Milavetz, P. A. v. United States, 559 U. S. 229, 234, 248-249 (2010) (considering an as-applied preenforcement challenge brought under the First Amendment). Based on these considerations, we conclude that plaintiffs’ claims are suitable for judicial review (as one might hope after 12 years of litigation).

Ill

Plaintiffs claim, as a threshold matter, that we should affirm the Court of Appeals without reaching any issues of constitutional law. They contend that we should interpret the material-support statute, when applied to speech, to require proof that a defendant intended to further a foreign terrorist organization’s illegal activities. That interpretation, they say, would end the litigation because plaintiffs’ proposed activities consist of speech, but plaintiffs do not intend to further unlawful conduct by the PKK or LTTE.

We reject plaintiffs’ interpretation of §2339B because it is inconsistent with the text of the statute. Section 2339B(a)(l) prohibits “knowingly” providing material support. It then specifically describes the type of knowledge that is required: “To violate this paragraph, a person must have knowledge that the organization is a designated terrorist organization . . . , that the organization has engaged or engages in terrorist activity ... , or that the organization has engaged or engages in terrorism ....” Ibid. Congress plainly spoke to the necessary mental state for a violation of § 2339B, and it chose knowledge about the organization’s *17connection to terrorism, not specific intent to further the organization’s terrorist activities.

Plaintiffs’ interpretation is also untenable in light of the sections immediately surrounding § 2339B, both of which do refer to intent to further terrorist activity. See § 2339A(a) (establishing criminal penalties for one who “provides material support or resources . . . knowing or intending that they are to be used in preparation for, or in carrying out, a violation of” statutes prohibiting violent terrorist acts); § 23390(a)(1) (setting criminal penalties for one who “unlawfully and willfully provides or collects funds with the intention that such funds be used, or with the knowledge that such funds are to be used, in full or in part, in order to carry out” other unlawful acts). Congress enacted §2339A in 1994 and §2339C in 2002. See § 120005(a), 108 Stat. 2022 (§ 2339A); § 202(a), 116 Stat. 724 (§ 2339C). Yet Congress did not import the intent language of those provisions into §2339B, either when it enacted §2339B in 1996, or when it clarified § 2339B’s knowledge requirement in 2004.

Finally, plaintiffs give the- game away when they argue that a specific intent requirement should apply only when the material-support statute applies to speech. There is no basis whatever in the text of § 2339B to read the same provisions in that statute as requiring intent in some circumstances but not others. It is therefore clear that plaintiffs are asking us not to interpret § 2339B, but to revise it. “Although this Court will often strain to construe legislation so as to save it against constitutional attack, it must not and will not carry this to the point of perverting the purpose of a statute.” Scales v. United States, 367 U. S. 203, 211 (1961).

Scales is the case on which plaintiffs most heavily rely, but it is readily distinguishable. That case involved the Smith Act, which prohibited membership in a group advocating the violent overthrow of the government. The Court held that a person could not be convicted under the statute unless he had knowledge of the group’s illegal advocacy and a specific *18intent to bring about violent overthrow. Id., at 220-222, 229. This action is different: Section 2339B does not criminalize mere membership in a designated foreign terrorist organization. It instead prohibits providing “material support” to such a group. See infra, at 26, 39. Nothing about Scales suggests the need for a specific intent requirement in such a case. The Court in Scales, moreover, relied on both statutory text and precedent that had interpreted closely related provisions of the Smith Act to require specific intent. 367 U. S., at 209, 221-222. Plaintiffs point to nothing similar here.

We cannot avoid the constitutional issues in this litigation through plaintiffs’ proposed interpretation of § 2339B.3

IV

We turn to the question whether the material-support statute, as applied to plaintiffs, is impermissibly vague under the Due Process Clause of the Fifth Amendment. “A conviction fails to comport with due process if the statute under which it is obtained fails to provide a person of ordinary intelligence fair notice of what is prohibited, or is so standard-less that it authorizes or encourages seriously discriminatory enforcement.” United States v. Williams, 553 U. S. 285, 304 (2008). We consider whether a statute is vague as applied to the particular facts at issue, for “[a] plaintiff who engages *19in some conduct that is clearly proscribed cannot complain of the vagueness of the law as applied to the conduct of others.” Hoffman Estates v. Flipside, Hoffman Estates, Inc., 455 U. S. 489, 495 (1982). We have said that when a statute “interferes with the right of free speech or of association, a more stringent vagueness test should apply.” Id., at 499. “But 'perfect clarity and precise guidance have never been required even of regulations that restrict expressive activity.’” Williams, supra, at 304 (quoting Ward v. Rock Against Racism, 491 U. S. 781, 794 (1989)).

The Court of Appeals did not adhere to these principles. Instead, the lower court merged plaintiffs’ vagueness challenge with their First Amendment claims, holding that portions of the material-support statute were unconstitutionally vague because they applied to protected speech — regardless of whether those applications were clear. The court stated that, even if persons of ordinary intelligence understood the scope of the term “training,” that term would “remai[n] impermissibly vague” because it could “be read to encompass speech and advocacy protected by the First Amendment.” 552 F. 3d, at 929. It also found “service” and a portion of “expert advice or assistance” to be vague because those terms covered protected speech. Id., at 929-930.

Further, in spite of its own statement that it was not addressing a “facial vagueness challenge,” id., at 929, n. 6, the Court of Appeals considered the statute’s application to facts not before it. Specifically, the Ninth Circuit relied on the Government’s statement that §2339B would bar filing an amicus brief in support of a foreign terrorist organization— which plaintiffs have not told us they wish to do, and which the Ninth Circuit did not say plaintiffs wished to do — to conclude that the statute barred protected advocacy and was therefore vague. See id., at 930. By deciding how the statute applied in hypothetical circumstances, the Court of Appeals’ discussion of vagueness seemed to incorporate elements of First Amendment overbreadth doctrine. See id., *20at 929-930 (finding it “easy to imagine” protected expression that would be barred by §2339B (internal quotation marks omitted)); id., at 930 (referring to both vagueness and overbreadth).

In both of these respects, the Court of Appeals contravened the rule that “[a] plaintiff who engages in some conduct that is clearly proscribed cannot complain of the vagueness of the law as applied to the conduct of others.” Hoffman Estates, supra, at 495. That rule makes no exception for conduct in the form of speech. See Parker v. Levy, 417 U. S. 733, 755-757 (1974). Thus, even to the extent a heightened vagueness standard applies, a plaintiff whose speech is clearly proscribed cannot raise a successful vagueness claim under the Due Process Clause of the Fifth Amendment for lack of notice. And he certainly cannot do so based on the speech of others. Such a plaintiff may have a valid overbreadth claim under the First Amendment, but our precedents make clear that a Fifth Amendment vagueness challenge does not turn on whether a law applies to a substantial amount of protected expression. See Williams, supra, at 304; Hoffman Estates, supra, at 494-495, 497. Otherwise the doctrines would be substantially redundant.

Under a proper analysis, plaintiffs’ claims of vagueness lack merit. Plaintiffs do not argue that the material-support statute grants too much enforcement discretion to the Government. We therefore address only whether the statute “provide[s] a person of ordinary intelligence fair notice of what is prohibited.” Williams, 553 U. S., at 304.

As a general matter, the statutory terms at issue here are quite different from the sorts of terms that we have previously declared to be vague. We have in the past “struck down statutes that tied criminal culpability to whether the defendant’s conduct was ‘annoying’ or ‘indecent’ — wholly subjective judgments without statutory definitions, narrowing context, or settled legal meanings.” Id., at 306; see also Papachristou v. Jacksonville, 405 U. S. 156, n. 1 (1972) (hold*21ing vague an ordinance that punished “vagrants,” defined to include “[r]ogues and vagabonds,” “persons who use juggling,” and “common night walkers” (internal quotation marks omitted)). Applying the statutory terms in this action — “training,” “expert advice or assistance,” “service,” and “personnel” — does not require similarly untethered, subjective judgments.

Congress also took care to add narrowing definitions to the material-support statute over time. These definitions increased the clarity of the statute’s terms. See § 2339A(b)(2) (“ ‘training’ means instruction or teaching designed to impart a specific skill, as opposed to general knowledge”); §2339A(b)(3) (“‘expert advice or assistance’ means advice or assistance derived from scientific, technical or other specialized knowledge”); §2339B(h) (clarifying the scope of “personnel”). And the knowledge requirement of the statute further reduces any potential for vagueness, as we have held with respect to other statutes containing a similar requirement. See Hill v. Colorado, 530 U. S. 703, 732 (2000); Posters ‘N’ Things, Ltd. v. United States, 511 U. S. 513, 523, 526 (1994); see also Hoffman Estates, supra, at 499.

Of course, the scope of the material-support statute may not be clear in every application. But the dispositive point here is that the statutory terms are clear in their application to plaintiffs’ proposed conduct, which means that plaintiffs’ vagueness challenge must fail. Even assuming that a heightened standard applies because the material-support statute potentially implicates speech, the statutory terms are not vague as applied to plaintiffs. See Grayned v. City of Rockford, 408 U. S. 104,114-115 (1972) (rejecting a vagueness challenge to a criminal law that implicated First Amendment activities); Scales, 367 U. S., at 223 (same).

Most of the activities in which plaintiffs seek to engage readily fall within the scope of the terms “training” and “expert advice or assistance.” Plaintiffs want to “train members of [the] PKK on how to use humanitarian and interna*22tional law to peacefully resolve disputes,” and “teach PKK members how to petition various representative bodies such as the United Nations for relief.” 552 F. 3d, at 921, n. 1. A person of ordinary intelligence would understand that instruction on resolving disputes through international law falls within the statute’s definition of “training” because it imparts a “specific skill,” not “general knowledge.” §2339A(b)(2). Plaintiffs’ activities also fall comfortably within the scope of “expert advice or assistance”: A reasonable person would recognize that teaching the PKK how to petition for humanitarian relief before the United Nations involves advice derived from, as the statute puts it, “specialized knowledge.” § 2339A(b)(3). In fact, plaintiffs themselves have repeatedly used the terms “training” and “expert advice” throughout this litigation to describe their own proposed activities, demonstrating that these common terms readily and naturally cover plaintiffs’ conduct. See, e. g., Brief for Plaintiffs 10, 11; App. 56, 58, 59, 61, 62, 63, 80, 81, 98, 99, 106, 107, 117.

Plaintiffs respond by pointing to hypothetical situations designed to test the limits of “training” and “expert advice or assistance.” They argue that the statutory definitions of these terms use words of degree — like “specific,” “general,” and “specialized” — and that it is difficult to apply those definitions in particular cases. See Brief for Plaintiffs 27 (debating whether teaching a course on geography would constitute training); id., at 29. And they cite Gentile v. State Bar of Nev., 501 U. S. 1030 (1991), in which we found vague a state bar rule providing that a lawyer in a criminal case, when speaking to the press, “may state without elaboration . . . the general nature of the . . . defense.” Id., at 1048 (internal quotation marks omitted).

Whatever force these arguments might have in the abstract, they are beside the point here. Plaintiffs do not propose to teach a course on geography, and cannot seek refuge in imaginary cases that straddle the boundary between “spe*23cific skills” and “general knowledge.” See Parker v. Levy, 417 U. S., at 756. We emphasized this point in Scales, holding that even if there might be theoretical doubts regarding the distinction between “active” and “nominal” membership in an organization — also terms of degree — the defendant’s vagueness challenge failed because his “case presented] no such problem.” 367 U. S., at 223.

Gentile was different. There the asserted vagueness in a state bar rule was directly implicated by the facts before the Court: Counsel had reason to suppose that his particular statements to the press would not violate the rule, yet he was disciplined nonetheless. See 501 U. S., at 1049-1051. We did not suggest that counsel could escape discipline on vagueness grounds if his own speech were plainly prohibited.

Plaintiffs also contend that they want to engage in “political advocacy” on behalf of Kurds living in Turkey and Tamils living in Sri Lanka. 552 F. 3d, at 921, n. 1. They are concerned that such advocacy might be regarded as “material support” in the form of providing “personnel” or “service[s],” and assert that the statute is unconstitutionally vague because they cannot tell.

As for “personnel,” Congress enacted a limiting definition in IRTPA that answers plaintiffs’ vagueness concerns. Providing material support that constitutes “personnel” is defined as knowingly providing a person “to work under that terrorist organization’s direction or control or to organize, manage, supervise, or otherwise direct the operation of that organization.” §2339B(h). The statute makes clear that “personnel” does not cover independent advocacy: “Individuals who act entirely independently of the foreign terrorist organization to advance its goals or objectives shall not be considered to be working under the foreign terrorist organization’s direction and control.” Ibid.

“[Sjervice” similarly refers to concerted activity, not independent advocacy. See Webster’s Third New International Dictionary 2075 (1993) (defining “service” to mean “the *24performance of work commanded or paid for by another: a servant’s duty: attendance on a superior”; or “an act done for the benefit or at the command of another”). Context confirms that ordinary meaning here. The statute prohibits providing a service “to a foreign terrorist organization.” §2339B(a)(l) (emphasis added). The use of the word “to” indicates a connection between the service and the foreign group. We think a person of ordinary intelligence would understand that independently advocating for a cause is different from providing a service to a group that is advocating for that cause.

Moreover, if independent activity in support of a terrorist group could be characterized as a “service,” the statute’s specific exclusion of independent activity in the definition of “personnel” would not make sense. Congress would not have prohibited under “service” what it specifically exempted from prohibition under “personnel.” The other types of material support listed in the statute, including “lodging,” “weapons,” “explosives,” and “transportation,” § 2339A(b)(l), are not forms of support that could be provided independently of a foreign terrorist organization. We interpret “service” along the same lines. Thus, any independent advocacy in which plaintiffs wish to engage is not prohibited by § 2339B. On the other hand, a person of ordinary intelligence would understand the term “service” to cover advocacy performed in coordination with, or at the direction of, a foreign terrorist organization.

Plaintiffs argue that this construction of the statute poses difficult questions of exactly how much direction or coordination is necessary for an activity to constitute a “service.” See Reply Brief for Petitioners in No. 09-89, p. 14 (hereinafter Reply Brief for Plaintiffs) (“Would any communication with any member be sufficient? With a leader? Must the ‘relationship’ have any formal elements, such as an employment or contractual relationship? What about a relationship through an intermediary?”). The problem with these *25questions is that they are entirely hypothetical. Plaintiffs have not provided any specific articulation of the degree to which they seek to coordinate their advocacy with the PKK and LTTE. They have instead described the form of their intended