Twitter, Inc. v. Taamneh, 598 U.S. 471 (2023) was decided by the Supreme Court of the United States on May 18, 2023 (No. 21-1496). The Court reversed the Ninth Circuit's judgment, 2 F.4th 871, holding the complaint failed to state a claim under § 2333(d)(2). Justice Thomas wrote for a unanimous Court; Justice Jackson filed a concurring opinion. Going forward, ATA plaintiffs suing infrastructure and platform providers must tie the defendant's assistance to the specific attack, or allege assistance so pervasive and systemic that the defendant aided every act of the organization. The Court expressly left open that selling unusually dangerous wares to a terrorist group, or consciously and selectively promoting a particular group's content, might support liability.
The question before the court
Does a social-media company aid and abet an act of international terrorism under 18 U.S.C. § 2333(d)(2) when it knowingly allows a foreign terrorist organization to use its generally available platform and recommendation algorithms, but does nothing more? What must a defendant have aided and abetted — the terrorist organization generally, or the specific attack that injured the plaintiff?
The governing rule
18 U.S.C. § 2333(d)(2), added by the Justice Against Sponsors of Terrorism Act (JASTA), Pub. L. No. 114-222, 130 Stat. 852, imposes secondary civil liability on any person "who aids and abets, by knowingly providing substantial assistance" the person who committed an act of international terrorism, where that act was committed, planned, or authorized by an organization designated a foreign terrorist organization under 8 U.S.C. § 1189. JASTA § 2(a)(5) identifies Halberstam v. Welch, 705 F.2d 472 (D.C. Cir. 1983), as "the proper legal framework." Halberstam requires (1) a wrongful act causing injury by the party aided, (2) general awareness of one's role in an overall illegal or tortious activity, and (3) knowing and substantial assistance to the principal violation, assessed against six substantiality factors. The Court read that framework against the common law and Nye & Nissen v. United States, 336 U.S. 613, 619 (1949), and Rosemond v. United States, 572 U.S. 65, 70 (2014).
How the court applied it
The Court accepted that plaintiffs satisfied Halberstam's first two elements — ISIS committed a wrong, and defendants knew they were playing some role in ISIS's enterprise — but held the third, knowing and substantial assistance, unmet. Justice Thomas emphasized what the complaint did not allege: plaintiffs never alleged that ISIS used the platforms to plan or coordinate the Reina attack, nor that the attacker Masharipov ever used Facebook, YouTube, or Twitter. The only affirmative conduct alleged was creating the platforms and setting up algorithms to display content relevant to user inputs and history. The Court treated the recommendation algorithms as part of that infrastructure, agnostic as to content, matching any content with any user more likely to view it. Because the claim rested on a failure to stop ISIS rather than affirmative misconduct, it sounded in passive nonfeasance, which demanded a strong showing of assistance and scienter. Two features defeated it. The relationship between defendants and the Reina attack was highly attenuated: defendants' posture toward ISIS was alleged to be no different from their posture toward their billion-plus other users. And plaintiffs identified no independent duty requiring communication-providing services to terminate customers discovered to be using the service for illicit ends. The Court also faulted the Ninth Circuit for framing substantial assistance around assistance to ISIS in general rather than with respect to the Reina attack.
What the court concluded
The Court reversed the Ninth Circuit's judgment, 2 F.4th 871, holding the complaint failed to state a claim under § 2333(d)(2). Justice Thomas wrote for a unanimous Court; Justice Jackson filed a concurring opinion. Going forward, ATA plaintiffs suing infrastructure and platform providers must tie the defendant's assistance to the specific attack, or allege assistance so pervasive and systemic that the defendant aided every act of the organization. The Court expressly left open that selling unusually dangerous wares to a terrorist group, or consciously and selectively promoting a particular group's content, might support liability.
From the opinion
- “The phrase “aids and abets” in § 2333(d)(2), as elsewhere, refers to a conscious, voluntary, and culpable participation in another's wrongdoing.” — Part III.A, concluding the Court's construction of the statutory phrase, 598 U.S. at 493.
- “The mere creation of those platforms, however, is not culpable.” — Part IV.A, rejecting the theory that building a general-purpose platform is itself assistance, 598 U.S. at 499.
- “insufficient to state a claim that defendants knowingly gave substantial assistance and thereby aided and abetted those wrongdoers' acts” — Part IV.A, on the platforms doing no more than transmitting information by billions of people, 598 U.S. at 503.
Why it matters for cyber conflict
It sets the baseline rule that providing neutral, generally available communications infrastructure — including algorithmic content matching — is not culpable participation in an attack, which is the analytical starting point for ATA claims against platforms, ISPs, hosting providers, and payment and messaging intermediaries.
Editorial note: this case note was drafted with AI assistance by the JLCW Research Desk, checked against the text of the opinion, and reviewed by a human editor before publication. Every quotation above is carried through from the opinion itself. See our editing policy.
Read the opinion: Twitter, Inc. v. Taamneh on CourtListener. This note is a summary prepared by the Journal, not legal advice, and not a substitute for the opinion itself.
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