Over the past several months, there has been increasing focus on terrorist use of social media. In the immediate aftermath of the execution of reporter James Foley by ISIL in July, the State Department acknowledged that, along with the Department of Defense, it reached out to social media sites, specifically Twitter and YouTube, to alert them to accounts posting the execution video and related images in violation of the sites’ “own usage polic[ies].”

This was not the first time that government officials had requested social media sites to suspend or shut down accounts affiliated with or related to Foreign Terrorist Organizations (“FTOs”). During the 2012 conflict between Israel and Hamas, both the Israeli Defense Forces and Hamas employed social media, including Twitter, to influence public perception. In response, seven House Republicans asked the FBI to force Twitter take down Hamas’s official account, as well those purported to belong to Hezbollah and al-Shabaab. Twitter ultimately suspended Hamas’s account in January 2014. In 2011, American officials announced that they were “looking closely” at al-Shabaab’s use of Twitter and exploring legal options to shut down related accounts. That same year, then-Senator Joe Lieberman requested that Twitter suspend all Taliban-related accounts.

In 2011, Glenn Greenwald speculated that the Department of Justice “could consider Twitter’s providing of a forum to a designated Terrorist organization to constitute the crime of ‘material support of Terrorism.’” The following year, the pro-Israel group Christians United for Israel (CUFI) began a petition campaign demanding that the U.S. government pursue charges against Twitter, under 18 U.S.C. § 2339A for providing service to Hamas. However, section 2339A would not provide the legal authority to prosecute social media sites because it requires specific intent to further the organization’s terrorist activities.

18 U.S.C. § 2339B, however, could provide the requisite legal authority, assuming the inquiry is limited only to accounts that purport to be or are clearly linked to FTOs (i.e. HSM Press, which is al-Shabaab’s media wing, or Andalus Media, the media wing of al-Qaeda in the Islamic Maghreb). Section 2339B outlaws “knowingly provid[ing] material support or resources to a foreign terrorist organization.” A conviction for providing material support to terrorists requires that the accused provided material support and that the accused knew the beneficiary of the support was a designated terrorist organization or knew that it engaged in terrorism. The statute defines material support as

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, weapons, lethal substances, explosives, personnel (1 or more individuals who may be or include oneself), and transportation, except medicine or religious materials.

In Holder v. Humanitarian Law Project, the Supreme Court clarified the term service (emphasized above), holding that the term “refers to concerted activity, not independent advocacy” and covers only “advocacy performed in coordination with, or at the direction of, a foreign terrorist organization.” The Court also found that Congress intended to reach only activities “directed to, coordinated with, or controlled by foreign terrorist groups.”

The Court’s use of these vague terms has only complicated the analysis of what actually constitutes material support under the statute. Particularly, what it means to coordinate with remains unclear. How the executive branch and courts interpret these terms will determine the extent to which the statute could be used to prosecute social media companies that allow designated FTOs to use their services.

It is easiest to dispense with any argument that the activities of social media companies are “directed to” or “controlled by” FTOs. As to the former, social media companies aim to serve as many people as possible; this is their business model. As to the latter, it would be absurd to purport that social media companies are controlled by FTOs, or that FTOs have any influence on the behavior of these corporations. Although the messages distributed through social media are indeed “controlled by” the FTO, the service itself—provision of a website through which FTOs spread these messages—is not. It is not as simple, however, to dismiss theories of liability based on the proposition that social media companies coordinate with FTOs.

One definition of “coordinate” is “bring[ing] into common action, movement or condition: regulat[ing] and combin[ing] in harmonious action.” (Webster’s Third New Int’l Dictionary, 1993). The government would have several bases for arguing that social media companies coordinate with FTOs: they provide these groups a platform from which to spread their message, recruit, and fundraise; they facilitate the distribution of FTO communications and propaganda; and they benefit from terrorist use of their product because it brings traffic that might not exist if not for the presence of such groups.

Despite the seeming ability of social media companies to prevent users from posting terrorist propaganda and/or flag and suspend FTO accounts (the blackout of the Foley execution suggests this is possible), social media companies may be able to defend any such allegation by highlighting their sheer size. These companies provide their services to hundreds of millions of individuals throughout the globe and would therefore have to allocate a large amount of resources to avoid any kind of facilitation. It is not clear that an impracticality defense would be effective, however. Moreover, actual practices weaken this defense: many social media companies routinely suspend some, but not all, of the FTO affiliated accounts on their websites (see here and here). Although these non-comprehensive suspension efforts are likely attributable to the sheer number of these types of accounts, it does suggest some sort of regulation or preferential treatment, even if that is not the true explanation. Additionally, there is some evidence that available technology could be used prevent users from posting terrorist propaganda (see here and here). However, as the definition of “coordination” requires some sort of affirmative action, that the companies have failed to implement such systems should not, but ultimately could, be sufficient to find coordination.

It is also unclear whether satisfying the coordination requirement is sufficient to satisfy the concerted activity requirement. The text and structure of the Court’s decision in Humanitarian Law Project suggests that proving coordination is all that is required under § 2339B because, once coordination exists, the activity is no longer independent of the FTO. However, if the concerted activity requirement is a separate prong, it is likely to be the biggest obstacle for any hypothetical prosecution. The government could contend that the companies’ failure to suspend FTO accounts is deliberate behavior the companies knew would assist the FTO. To rebut this assertion, the companies could contend there is nothing planned or deliberate about the way in which terrorist organizations use their product, at least on their part; rather, it is merely a result of the companies’ business models.

It is impossible to predict how courts would decide the aforementioned issues. However, the uncertainty suggests that prosecution of social media companies is not so outlandish that the government would never pursue that course of action, especially if the threat posed by terrorists on social media continues to grow.

Understanding that prosecution of social media companies under § 2339B is plausible, the next logical question is how far would this theory take us. For example, could § 2339B apply to private bus services or taxis that transport terrorist group members, or to telecommunications providers that carry their phone conversations? The short answer is yes, assuming certain facts exist. For example, if an FTO were to reserve a private bus but not disclose its identity, the company would not be liable. However, if the FTO were to identify itself in some way, § 2339B could easily provide the basis for criminal charges. The same rings true with taxis or telecommunications providers. The key to this inquiry, then, is whether the provider knows of the FTO’s identity and still provides the requested service.

What type of due diligence is required of companies or even individuals that provide services to a large population? Little guidance exists on the subject and what does exist, for example OFAC guidance, may not be appropriate. Imagine if Facebook, Twitter, Instagram, etc. were required to perform due diligence on each of its users before they could create an account—the impact on their business models would be catastrophic (not to mention the ensuing invasion of privacy). Additionally, despite the potential threat that results from terrorist groups using social media, other factors, such as counter-terrorism value and the First Amendment, warrant consideration. How courts, legislators, and the executive branch will weigh these factors remains to be seen.