Page:Twitter v. Taamneh.pdf/3

Syllabus

be accepted as immutable components” but should be “adapted as new cases test their usefulness in evaluating vicarious liability.” Id., at 489. Pp. 9–11.

(ii) Because the allegations here—involving international terrorist networks and world-spanning internet platforms—are a far cry from the facts of Halberstam, the Court must ascertain the basic thrust of Halberstam’s elements to determine how to adapt them to the facts of this case. To do so, the Court turns to the common law of aiding and abetting upon which Halberstam rested, and to which JASTA’s common-law terminology points. At common law, the basic “view of culpability” animating aiding and abetting liability is that “a person may be responsible for a crime he has not personally carried out if he helps another to complete its commission.” Rosemond v. United States, 572 U. S. 65, 70. However, the concept of “helping” in the commission of a crime or a tort has never been boundless and ordinarily requires some level of blameworthy conduct; those limits ensure that aiding and abetting does not sweep in mere passive bystanders or those who, for example, simply deliver mail that happens to aid criminals. In tort law, many cases have thus required a voluntary, conscious, and culpable participation in the wrongful conduct to establish aiding and abetting. In doing so, they further articulated Halberstam’s framework to capture those limits. As above, that framework requires that the defendant give knowing and substantial assistance to the primary tortfeasor; notably, courts often viewed those twin requirements as working in tandem, with a lesser showing of one demanding a greater showing of the other to establish a conscious, culpable participation in the tort. Pp. 11–16.

(iii) Halberstam differentiated types of aid along the same culpability axis that grounded the common law. And its six factors for “substantial assistance” call for the same balancing that courts had undertaken previously between the nature and amount of assistance and the defendant’s scienter. Pp. 16–17.

(2) The parties then vigorously dispute what precisely a defendant must aid and abet under §2333(d)(2). Plaintiffs assert that it is “the person,” while defendants insist that it is the “act of international terrorism.” That syntactic dispute makes little difference here, because aiding and abetting is inherently a rule of secondary liability for specific wrongful acts. In the tort context, liability is imposed only when someone commits (not merely agrees to commit) an actual tort. And in this case, the ATA limits that liability to injuries caused by an “act of international terrorism,” §2333(a). It thus is not enough for a defendant to have given substantial assistance to a transcendent enterprise. A defendant must have aided and abetted (by knowingly providing substantial assistance) another person in the commission of the