Cite as: 598 U. S. ____ (2023) 1 Opinion of the Court NOTICE: This opinion is subject to formal revision before publication in the United States Reports. Readers are requested to notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, pio@supremecourt.gov, of any typographical or other formal errors. SUPREME COURT OF THE UNITED STATES _________________ No. 21–1496 _________________ TWITTER, INC., PETITIONER v. MEHIER TAAMNEH, ET AL. ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT [May 18, 2023] JUSTICE THOMAS delivered the opinion of the Court. Under 18 U. S. C. §2333, United States nationals who have been “injured . . . by reason of an act of international terrorism” may sue for damages. §2333(a). They are not limited to suing the individual terrorists or organizations that directly carried out the attack, however. That is because §2333(d)(2) also imposes civil liability on “any person who aids and abets, by knowingly providing substantial assistance, or who conspires with the person who committed such an act of international terrorism.” Victims of terrorist acts therefore may seek to recover from those who aided and abetted the terrorist act that injured them. The plaintiffs (who are respondents) contend that they have stated a claim for relief under §2333(d)(2). They were allegedly injured by a terrorist attack carried out by ISIS. But plaintiffs are not suing ISIS. Instead, they have brought suit against three of the largest social-media companies in the world—Facebook, Twitter (who is petitioner), and Google (which owns YouTube)—for allegedly aiding and abetting ISIS. As plaintiffs allege, ISIS has used defendants’ social-media platforms to recruit new terrorists